Idling and acceleration problems

perk · 02-20-06, 08:38 PM

I took it to a shop here in Redlands to test TPS, MAF, IAC, and run a complete computer diagnostic. Everything was within parameters except..................... TPS was improperly set at 9 degrees. He set it back to 5.5-6 degrees and its now idling at 650 rpm and acceleration and shifting are more responsive and engine feels smoother. I haven't gone on an extended drive yet, but hopefully problem solved.

Good call Beo, CJF, and of course Robbie, you guys had TPS in mind all along.

Thanks to all who lent their expertise,
Ted

perk · 03-24-06, 02:52 PM

Ugly head reared again....over the last two weeks, a low idle (3-400rpm) has occurred a few times. Unlike before, it is not stalling or even running rough once dropped down, likely the result of the TB cleaning and TPS adjustment. Each time, if I turn the engine off and restart, the idle goes back to normal.

When I discussed this with the owner of the shop who did the TPS adjustment, he said that the computer didn't show anything out of perameter and that they did physically check the resistances on the MAF, IAC, and TPS. He also said that even though the MAF, IAC, TPS all tested OK, there still could be a problem with one of these because they will test/behave differently under different driving conditions.

Today, while on the freeway, I turned on the AC, for the first time in many months. When I got to the end of the offramp, it was doing the same high idle business as before where it's at about 1200 rpm, wanting to pull away and when placed in P or N the engine starts revving to about 2200 than falling back down to 1200 over and over. I turned the engine off, restarted and back to normal.

Given these new data points, where's the next best place to look? Could O2 sensors have anything to do with this, just turned 100K on the clock and they're original?

Thanks,
Perk

CJF · 03-24-06, 03:49 PM

It not the O2 sensors.

While neither is good, the surging idle would concern me more than the low one for now; I'd go after that first.

Off the top of my head, the only things I can think of that can do what you're describing are sticking linkages or (again...) the TPS.

Anyone else??

Curtis

perk · 03-26-06, 03:47 PM

Thanks CJF,

Could there be something wrong with the TPS even though it's in the proper position and the resistances were all ok? How does the TPS work, sure seems like an odd little item.

Does anyone else have any ideas about this?

Many thanks in advance,
Perk

CJF · 03-26-06, 04:08 PM

By "proper position", you mean the ohmmeter deflection test with a feeler gauge at the back of the throttle body? If you've done that and the other resistance tests, then I'm afraid I'm out of good ideas.

Now bad ideas, on the other hand, I've got plenty of.

One would be to rotate the TPS to increase the deflection distance a little bit anyway, just to see if it changes anything. I actually think I'd try that if I were in your shoes, since too small a gap could definitely be causing the high idle. (Which again more immediately concerns me than the low idle.)

Keep in mind this whole (TPS) direction of inquiry might be a dead end. I just got nothin' else.

I feel for ya, man; hang in there.

Curtis

CJF · 03-26-06, 04:26 PM

Re-reading this thread, I think my "bad idea" in the above post is probably just beating a dead horse.

This is really bugging me though: I simply cannot imagine what would allow the motor to cycle from 1200-2200 (

!) rpms in park without your foot on the gas!

desmocruiser · 03-27-06, 03:14 PM

Would you need to reset the ecu by pulling the fuse after each corrective step? It probably doesn't make that big of a difference, I just did it during my search to be thorough.

perk · 03-27-06, 07:53 PM

What are the steps to pulling the fuse?

desmocruiser · 03-28-06, 10:10 PM

The underhood fuse box contains the fuse, I just pulled for ~60 seconds, replaced and then allowed to idle for several minutes to relearn any programming. Definitely will not FIX anything just allow any fixes to better match up to the ecu program.

hurricanesteve · 03-29-06, 10:38 AM

another data point, since mine was acting a little weird (97 lx450) after a HG job:

mine was iding a little rough and higher than normal: obd2 laptop software showed 12% throttle at idle. I didn't have an FSM, but based on your previous post i turned it down to 6%. it was great for a couple of days, but now it's dropping a little under 600 RPM at idle, so i ponied up $10 for the online FSM. that says;: "7-11% at idle" at least for a 97.

I'm going to follow the TPS adjustment procedure per the manual with an ohmmeter to see if it helps.

And the a/c compressor does tend to shoot the RPMs up quite a ways on mine...not sure it goes to 2200, but i'll watch it more closely and post what it does.

fj40fax · 11-09-06, 02:00 PM

Any resolution to this problem?

Thanks,
Fax

perk · 11-16-06, 10:11 PM

Update...I finally got it back in the shop and they had a hard time with diagnosis, and finally decided IAC was the problem, and the TPS was fine. With the much greater number of replaced TPS's vs. IAC's reported on the forum and $68 vs. $335 (Cruiserdan), I decided to have them replace the TPS first. I picked up a TPS from local dealer ($91) took it by shop. They installed it, and later informed me that the idling problem was unchanged, still moving around. With feelings of

I orded the IAC from Dan. Since it wouldn't get to me until a few days later I picked up the cruiser from the shop intending to bring it back once the new IAC arrived. Well, I've had it for a few days now and the idle seems to be perfect. It's high (1000-1200) at first when cold, but gets down to 800 and then begins resting at 600-700 once warm. I've been driving heavy on the gas, which often set it off before, and no problems, it hasn't dropped below 600 yet. In fact I just played around in 4lo last night, something that usually got the idle to start dropping, and it stayed right around 650 except one time it got down to 500, but shortly corrected back. It looks like the TPS was the problem after all. If it does start acting up again, I'll give another update.

Thanks to all who have tried to help...I know some of you are sitting back thinking...isn't that what I've been saying all along?

Perk

CJF · 11-16-06, 11:23 PM

Quote:

Originally Posted by perk

It looks like the TPS was the problem after all.

Good on ya for reporting back!!

Keep us posted,

Curtis

perk · 12-01-06, 11:51 PM

Well the TPS did help but.....the intermittent low idle (3-400) came back a few days after my last post. I had the new IAC put in so we'll see. No news will be good news.

Perk

IdahoDoug · 12-01-06, 11:56 PM

Wat'cha doing with all your old parts? Want to contribute them to the Mud experimental parts depot?

DougM

beno · 12-02-06, 05:46 AM

Quote:

Originally Posted by IdahoDoug

Wat'cha doing with all your old parts? Want to contribute them to the Mud experimental parts depot?

DougM

If this is for real (

), I have tons to donate.

perk · 12-06-06, 05:30 PM

Well...it looks like I've got a functioing TPS and IAC sittin in the garage, so I'll think about it Doug

The IAC did nothing to correct the low idle, in fact it seems to drop down a little more since the install. So any other ideas considering the replaced TPS and IAC? I was told by the mechanic that the wiring harness was ok.

Thanks alot,
perk

CJF · 12-06-06, 08:29 PM

No more high idle, at least??

Curtis

Beowulf · 12-06-06, 08:30 PM

Quote:

Originally Posted by perk

Well...it looks like I've got a functioing TPS and IAC sittin in the garage

Please post the part numbers of each.

-B-

perk · 12-18-06, 10:48 AM

TPS: 89452-22090
IAC: 22270-66011

The surging high idle showed itself again (after a 40 mile hwy drive with the AC on). The low idle (400 rpm) shows itself nearly every time I take it out. I noticed during the surging idle episode that acceleration was off too, like it was lightly to moderately bogged down.

I'm a little hesitant to take it back to the same shop. Am I wrong in thinking that there are very clear cut/black and white methods for testing the TPS and IAC to show if they are malfunctioning, and the shop is suspect for not doing so? The owner suggests I bring it back so they can continue diagnosing, he keeps bringing up the computer as the possible culprit.

Any additional thoughts/advice would be very appreciated.

Thanks,
Perk

perk · 12-23-06, 11:19 AM

Another observation...gas mileage has been down for a while (11 mpg around town) and today, I noticed that the exhaust smelled like gas upon startup. It looks like from the lack of response, people are out of ideas. Do these two additional points bring up any ideas.....?

Thanks,
Perk

landtank · 12-23-06, 11:42 AM

I briefly scanned the past posts so if this is a repeat sorry. At this point I'd replace both O2 sensors. I had similar issues with dead spots and then the Front sensor threw a code and all is well since replacing.

If they haven't been done yet then it's not a complete waste of time and if they have been done confirm they are OEM.

perk · 01-28-07, 04:33 PM

I relplaced Both 02 sensors replaced (OEM) about two weeks ago. I've put around 200 miles on since and......low idle still there. I thought it was gone at first, as it idled nearly perfectly (dropped down once or twice, but corrected itself) for the first couple of days. Just over the last couple days, its dropping low (400) alot.

Any other ideas?

O2 sensors came of without too much difficulty. Bolts were a bit rusty, but got them off without any pre-treatment or nut breaker. Out of curiosity, I called the dealer to find out their labor charge...$275. When I asked about the high price for the simple procedure, was told that part of the price was related to something they do with the computer. This got me wondering if there is something necessary to do related to the computer other than clearing any codes that may be present.

Thanks
perk

RavenTai · 01-28-07, 04:54 PM

Quote:

Originally Posted by perk

Am I wrong in thinking that there are very clear cut/black and white methods for testing the TPS and IAC to show if they are malfunctioning, and the shop is suspect for not doing so?

yes if there are hard faults they can be quickly go/no-go tested but intermittent faults are difficult.

Quote:

Any additional thoughts/advice would be very appreciated.

start working on your own truck, the major reason this has gone on for so long is that you are not doing the things recommended here.

CJF · 01-28-07, 08:56 PM

Quote:

Originally Posted by perk

When I asked about the high price for the simple procedure, was told that part of the price was related to something they do with the computer.

No, there's nothing you need to do related to the computer.

I know your journey must seem frustrating, but I think you're doing everything right at this point. I'd say just keep driving it and enjoying it, and take care of any suspect maintenance items yourself as you have the time/money. For example: Throttle body cleaning? Injector rebuild? (I can't recall anymore what's been done already and what hasn't...)

Keep hangin' in there,

Curtis

perk · 01-28-07, 10:45 PM

Thanks CJF and Raventai for the feedback. Within the last year I've performed complete tune up including wires and throttle body removal and cleaning. I probably should have gotten the necesarry tools and tested the TPS and IAC myself, but I thought I'd give the professionals a shot...oh well...I don't regret replacing these parts as I do notice an improvement in performance (when idle is not acting up).

CJF do you think plugged injectors could cause the idle problem? That is a mainenance item I would like to do...it looks like it might take more time than I have for it, might end up taking it in for that...we'll see...I would like to do it.

Raventai, I think I've faithfully pursued every avenue suggested, and with the exception of the TPS and IAC testing, have done all of the work myself. In fact I have done all of the other work on my truck myself with the help of this board, the FSM, and of course Dan. Actually its a fairly substantial list for someone as myself who had never done any work himself prior to purchasing the 80. Anyways...if you notice a suggestion for my idle problem from a previous post that I missed please point it out. I have read many of your posts and definetely value your opinion on all things mechanical.

Additional thoughts: Could a bad fuel filter cause idle problem? Around town mpg is really bad, 9-11, but got 16 out on the highway. Could the low mpg and idle problem be related? Could the fuel mixture be too rich or lean? How is this tested? The mechanic that tested the TPS and IAC thought the computer may be the problem...how is the computer tested?

Additional thoughts and suggestions will be greatly appreciated...

perk

landtank · 01-29-07, 07:48 AM

Have you checked your coolant level? I had a low coolant level that was causing issues with the ECM temp sensor and the truck's idle was erratic.

RavenTai · 01-29-07, 06:50 PM

Ok the previews posts lead me to think you had paid someone to clean the TB witch means there was no garontee it actually happened

I don't think the computer is it, they very rarely go bad. you test the computer by testing or replacing everything else and then the ECU as a last resort, mechanics too often jump the gun and go to the ECU too early. I would shotgun the harness before I shotguned on a ECU.

This still stinks of TPS But the TPS itself has been replaced that points to the wiring between it and the ECU, you say use of 4lo and heavy throttle application cause it to show, that points to harness, in both cases the engien moves more in relation to the firewall therefore flexing the harness. you have not yet taken it apart and closely examined the wires. and yes there can be problems inside just from heat with no apparent outside damage, the wire insulation gets soft and the wires come through and randomly short to each other.

before you go there check a few things, are the return springs on the TB in good shape? put some light spray lube on the throttle cable at both ends and try to work it into the cable, do a spot check on the TPS idle switch, at this point you don't have to do the full check, just make sure you have continuity at idle and not when the throttle is opened, I would do this check both cold and after a good highway run, some other goofy things could be a loose throttle plate giving an inconsistent closed position witch would give the TPS a hard time, or a worn throttle body where the throttle plate shaft passes through

one other thing does it happen only in cool weather? like 25-45 degrees?

BPMOU · 03-05-07, 10:35 PM

I have been following this post because I have a similar problem. My 97 FZJ80 typically idles while in P at a hair over 600 and then a hair below when in drive. Lately when I start it in the morning it idles a little rough and then smooths out as it warms up. The last couple of days I have noticed that when I am coming to a stop after going 45+ mph the rpm drops to a hair over 400 rpm by the time I completely stop. It doesn't seem to want to stall, but it is idling really low. I looked at the air intake and didn't see any cracks. Thoughts?

Jomama · 03-13-07, 03:22 PM

Quote:

Originally Posted by BPMOU

I have been following this post because I have a similar problem. My 97 FZJ80 typically idles while in P at a hair over 600 and then a hair below when in drive. Lately when I start it in the morning it idles a little rough and then smooths out as it warms up. The last couple of days I have noticed that when I am coming to a stop after going 45+ mph the rpm drops to a hair over 400 rpm by the time I completely stop. It doesn't seem to want to stall, but it is idling really low. I looked at the air intake and didn't see any cracks. Thoughts?

I've got a similar prob that showed up about 2 weeks ago...

Coincided with a real harsh cold snap, but even when its warmed up since its continued...

Started truck up to warm it up 2weeks ago, come back 10 min later and immediately notice a off/rough idle, had not noticed it the previous day.

Initially attributed it to the extreme cold (like > -30 below windchill)

But even after the truck warmed up to full op temp, it was stumbling at every stoplight (around 500 rpm).. After a few seconds of being stopped it seemed to balance out.

Now its still got the rough idle when I warm it up, the stop light idle is even worse (and wierd)..

As I'm braking, decelerating, the RPM's drop kinda fast, and goes into the rough idle before I'm even stopped (bouncing around 500rpm)... But as soon as I'm stopped for a few seconds, it tends to smooth out and level out at 600rpm... w/out throttle, and regardless of if I still have foot on brake or not (have been testing that specifically)...

And now the last day or too, this seems to be getting worse, with a more sporadic idle as I'm slowing to a stop... Really lugging, bouncing between 300 - 500rpm... But its still going back to a normal idle a few seconds after I stop

However just pulling into my parkinglot over lunch, it lugged so hard while I was slowing, and turning into the lot at the same time it completely stalled... Powersteering putting more stress on the lugging motor was my guess??

I did not do anything to it maint wise recently, so I know I didnt mess w/anything to cause this... It just showed up... Last maint was a P/S line break and get worked on last Nov... And its kinda on the cold side here right now, terrible weather to troubleshoot in outside...

I've looked at the rough idle threads, so I do have an idea where to start..

The fact that the worst part of the problem only occurs while stopping makes it hard to put my finger onto where to focus my efforts tho...