Flat Spot at 2000 RPM's

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Jun 13, 2003
Omaha Nebraska
Ok, so I recently did my own tune up on the beast and I still get a "Flat Spot" around 2k. Once I get her over that hump she shines like a gem though! Granted its not bad and when I need to get on her horses from a dead start you don't notice it or can't feel it for that matter. Anyone have thoughts on this or have had somewhat the same issue. Buddy will be doing a diagnostic check on it (has his own reader thank god ;)) to make sure numbers are where they should be. Oh, also I've tried running a higher octane for the past several months with no change to this.

Advance the timing to about 8Deg at idle. I brought mine alive.

94' FJ80
I think kurt is on it.
look on the lower side in the hose form mass air flow to the throttle body and you are probably cracked on the lower side.

Thanks for the replies. Kurt I think your on the money. I'll check tonight.

Tank,from your PM, if your hose is cracked, you will need to replace it.
Remove it and flex it and look for cracks.
Seal one end and blow the other end.
I used the compressor to test mine.
Sorry, don't mean to be stupid but the "hose" i thought we were talking about coming going to TB is fine. I hope I'm not confusing "hoses" here. Can anyone take a quick pic to confirm which one we are talking about. If not, don't worry about it. I'll move on to plan B = -)
Ok I'm the Du Mass :slap:

Thanks Kurt for the Pic...well, on to plan B. My hose is fine, no cracks.

If you are looking for plan b, this may do nicely. Go back to the same hose - yes the big pleated boy - and unscrew the wire clamp on the throttle body side. Pull the hose and look in there. See all that black tarry stuff all built up around the butterfly valve's bottom surface? Yep. Open the throttle and see there's more of it stuck all around the throttle valve's seat? Yep. Go get some fuel injection cleaner in a spray can and a tooth brush and some rags. Jamb the throttle fully open and commence to cleaning.

You'll have no more hump at 2000 - it will change to a jump.
Yeah thats gonna be my next plan of action. Actually I checked this the last time I had the hose off (sister had same problem with her Pathfinder) It looked ok for the most part. Still gonna do the clean. My brother has the tools to do the "full" injection system clean. He claims its a 3 part system that when he does it, he's gotta change oil because of how black it gets from the cleaner? Oh well, I trust him. Now just have to find time to do the :banana: job....

Regarding the cleaning of the intake. I recently did this and was not happy with just reaching through the butterfly valve with a toothbrush so I also removed the butterfly valve section which allowed me to reach in much further to the individual upper chambers of the intake. Now I'm wondering if I should go one step further and remove that upper part of the intake so I can thoroughly clean each chamber all the way to the block? Is this a worthwhile idea and if so, are there any dangers I should be aware of?No FSM but it looked pretty straight forward.

Thnx, Vince
Yes, it's pretty easy. Do the injectors and replace the PHH while you're at it.
Can you enlighten me a lil on how to clean the injectors (no fsm). I have looked at the PHH and it looks fine but if having the whole intake off is gonna make it that much more accessible then I may as well tackle it.
One last question. Should I take the manifold off as 3 seperate pieces (butterfly part, upper half, lower half)? Or is there a better, quicker way?

Thnx, Vince
Pull the injectors and send them off to be cleaned and balanced. There are several companies that do this. I had mine done for ~$60 + shipping. Replace the rubber grommets between the injectors and the intake.

I removed the intake in 3 pieces. You can clean out the chambers that way.

Yes, do the hose. Do all of them that you can reach.
Removing the intake chamber will not help much for the PHH. Removing the intake manifold would. I didn't replace my PHH when I had the chamber off but was planning on it if it was easyer to get to. It wasn't.

I was going to have my injectors cleaned when I had the chamber off but was advised not to mess with them. With my millage and age, the wiring harness wires tend to get brittle and brake. I didn't want to mess with a new harness at that time so I left them alone.
You should/need to remove the intake chamber to clean the carbon out. The EGR port, where the carbon comes from, gets thick with carbon.

A FSM would be good to have for this job.
LANDTOY, I agree. After looking closer at it, I dont think I could remember exactly where everything goes once it comes time to put it all back. Gonna wait 'til I get fsm for the birf repack.

Just to report back guys....injectors flushed and like the article(www.safari4x4.com.au/80scool/t.../flat_spot.html )there was a difference. Sooooooooo over the next month I'm gonna try and flush it two more times to see if it keeps getting better. LOTS of carbon coming out as we were flushing it. Also idles better...


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