Rough Idle at stops, yes i have searched, help (1 Viewer)

[Tbkw01]

I have searched for this and want some ideas. I have looked for cracked hoses and did the unplug the battery and then replug the battery trick, as discussed in earlier posts. Before I take it to a real mechanic and pay real prices for maintenance is there anything else that i can check? Additional info, I have a 94 with 144k miles. I recently replaced the plugs and wires. When i accelerate it does seem to go away. When stopped at a light (in drive) it idles and i get a very momentary drop in rpm which then returns to normal for a few seconds and then the cycle repeats. There is no way that i messed up the timing right? could it be something big wrong with the engine, misfiring?

 

[86tuning]

When did this start? Did you do plugs and wires as an attempt to repair? What brand wire set?

 

[jcarter]

Now way you messed up the timing, right!

Check your small vacuum hoses. Many times I mess with the plug/wire side of the engine, it runs bad after I do the work, I look and find a small vacuum hose I forgot. Look at the vacuum diagram.

Once I put fuel vapor return line to the wrong spot. Look at the vacuum diagram TWICE.

A bad/intermittent idle isn't a big deal.

Joe

PS I've got a 92, 3FE, but principle is the same.

 

[Tbkw01]

Replaced non oem with all oem. I will check again but would a cracked vac line work intermittently? I did watch the engine as it idled. If there was a cracked hose would there be a sucking sound?

 

[CDFarmer]

Are you running a Toyota OE wire set - Denso plugs? As others have mentioned, aftermarket plug wires may be the culprit. Check the air intake boot for cracks. While the truck is running, see if you can duplicate the idle issue by moving the boot back and forth.
If all else fails, see if you can swap the idle speed control valve with a "known" correctly functioning one, there not cheap, so you would want to confirm yours is faulty. My 94' had a faulty idle speed control valve, my symptoms were identical to what you've describe.

 

[chairborne]

Not to jump on the bandwagon but since you presumably did remove the air intake tube my first guess is that it is cracked. Wrap the ridged section with duct tape and see if it helps.

 

[NorCalDoug]

just making sure...when I had similar symptoms, my air intake hose was cracked on the underside. It didn't look cracked until I removed it and carefully checked. While waiting for my replacement, I taped the hell out of it and it worked fine until my new one arrived.

 

[Tbkw01]

I will double check everything. The drop in rom is almost a ticking movement, very fast. Could it be a problem with the pistons? I just bought it about two months ago.

 

[Tbkw01]

Not to jump on the bandwagon but since you presumably did remove the air intake tube my first guess is that it is cracked. Wrap the ridged section with duct tape and see if it helps.

I will try this when I get home

 

[chairborne]

I will double check everything. The drop in rom is almost a ticking movement, very fast. Could it be a problem with the pistons? I just bought it about two months ago.

That sounds like the usual idle stumble caused by burned #5 or #6 injector wiring. I've fixed it on one of my 80s and am tackling it on my other one this weekend.

 

[mattafact]

Had the same problem on my 93. Did a full tuneup including O2 sensors, new intake tube, rotor, cap, plug, etc. Nothing. Then I figured it was the IAC but didn't want to spend insane amounts of money on replacing it. Bought a used TB from Torfab for a great price, problem solved.

 

[medtro]

Cleaned up oil in IAC fixed the idle problem for me.

 

[Tbkw01]

Cleaned the iac. Also took off the air duct and inspected it for cracks. None that I can see. Restarted it and it is worse. I think it must be the duct. I will taps the whole thing tomorrow and see if it fixes it. I know a 92 has a different engine but does it use the same iac? There is a 92 in the junkyard that I can rob from if I need to.

 

[Tbkw01]

Cleaned the iac. Also took off the air duct and inspected it for cracks. None that I can see. Restarted it and it is worse. I think it must be the duct. I will taps the whole thing tomorrow and see if it fixes it. I know a 92 has a different engine but does it use the same iac? There is a 92 in the junkyard that I can rob from if I need to.

tape it tomorrow...

 

[86tuning]

remove the intake boot/tube and bend it around to check for cracks.

duct tape makes a good temporary repair. The permanent fix is a new one, then you're good for years.

 

[Michael Hanson]

Hi, Adjust the valves. Mike

 

[jda81]

Is it when you are in park or on the breaks? I had a rough idle at stops but not in park all the vacuum lines were good replaced the booster breaks improved greatly and idle at stops fixed too.

 

[Tbkw01]

In both park and during stops while in drive. I wrapped the air duct in tape, no luck. I will clean the throttle today. If that doesn't work I will replace the vacuum hoses.

 

[Tbkw01]

In both park and during stops while in drive. I wrapped the air duct in tape, no luck. I will clean the throttle today. If that doesn't work I will replace the vacuum hoses.

then adjust the valves.

 

[CHibbard]

You don't mention if the CEL is on?

I've had the same condition for many months.

Last weekend I did a complete cleaning of the TB, EGR and Intake. The EGR port into the Intake was carbon plugged solid. 2 hours of heavy cleaning with brushes. TB was dirty as well. Cleaned all ports and the butterflies of any dirt. Had the injectors cleaned and serviced by RC Engineering (Torrance), new EGR and associated items with the EGR circuit, replaced all vac hoses, new TB/Intake/EGR gaskets. After all of this work, engine idles perfect, no CEL and no more stalls.

If air tube attached to the TB is cracked (even a hairline crack, letting in un-measured air) the engine will idle rough, stall and even throw a CEL. I did have this situation around 140K miles. New air tube from CDan fixed.

Tip: If you decide to start this project, it very well documented with the forum. Plus, take a ton pictures before you start the project. As well as during the project. You will need these pics to remind you what vac hose goes where