Fluctuating Timing

[Backlash2032]

Hey, I just swapped my 7m-GTE from my 1990 Supra which was wrecked into my new 1989 Supra, and there is ONE problem (so far...). When you first start the car, it seems to run great. Albeit a little sluggish on quick throttle blips. But my 7Ms have nearly always been like that when cold. Anyway, after a few minutes of running, the idle starts to come down.. And not like usually. It will drop down to 500-700 rpm and start loping like a big v8 with a huge cam. It actually sounds pretty sweet...

I thought it was timing, so I jumped Te1 and E1, and threw a timing light on it. While it's running smooth, its at a perfect 10* BTDC, but when it bogs out, timing jumps anywhere from 15-20* to 0*. Again, this is with Te1 and e1 jumpered. (sidenote: Is timing supposed to go up to roughly 25* when you rev it up to about 2000 with TE1 and E1 jumped?) No codes stored on the ECU, fresh knock sensor wiring, and with an engine that used to run absolutely perfect, no matter what temperature it was being ran in. Also, when driving, it just doesn't seem as quick doing just minor pulls to about 3.5k rpm.

Any ideas? I was thinking it might be the pickups in the CPS, but I'd like to get another opinion.

Also, mods = driftmotion FMIC, skimmed head and block with factory size MHG, walbro 255. Could a quarter tank of e85 mixed with a quarter tank of 87 octane do this? Should be roughly e40 by my calculations.

 

[Backlash2032]

Nobody? I've tried quite a few things. I've read oil in the CPS could do this.. So I checked that, bone dry. Wiggled the wiring to the CPS while it was bogging out and no help there.. Ditto for the coil packs. Filled up the tank with 87 octane (everything else is e10) so it should be about e20-30. Checked the coil packs for cracks, nothing. Pulled all of the spark plugs and they were all indicating a good burn.. There was some carbon around the outside but there was even when it was running right. I'm at a loss as to what this is.. Disconnected the TPS to see if maybe it was giving an incorrect signal, no change. Did the same with the knock sensors.. Same result.

The only thing I've managed to do today, was get my hopes up with oil in the rear 2 spark plug wells.. But even with that cleaned out there was no change. I've also figured out that for some reason, if you let it sit for a little bit it will run fantastic.. usually.. And then the second you turn it off and turn it back on (as if you filled up) it starts running terribly. Loping like it has a big cam at idle, and no power.

Could a walbro 255 + no afpr do this? If so.. I'm gonna be so pissed that I filled up today, because I can't afford an AFPR and I have a spare stock fuel pump...

 

[thevork]

When you have the stock FPR there is no need for an AFPR.

I had a similar problem once, I'll describe it but I doubt that this will solve your problem.
What happened to me was I installed a new engine (7Mgte) in my friends supra and tried to set the timing, but it was way off the scale.
So I took out the CPS and inserted it again just to be sure that the CPS is aligned/timed perfectly. After that timing was somewhat better at idle, but when revving I had problems similar to yours.
It turned out to be a problem with the throttle body. It was dirty inside AND near the springs where the lever is and that was causing the TB to not close fully. I could release the throttle and then push the lever with my thumb so the TB valve would close. After that, i removed and re-inserted the CPS again,cleaned the TB and everything was fine.

 

[Backlash2032]

Throttle body is clean and the timing is perfect at 10* when its running smooth, but when its running rough it fluctuates.

 

[CyFi6]

I am assuming no codes? Does it sound anything like this?
http://www.supramania.com/forums/sh...ng-a-f-ratio&p=1901623&viewfull=1#post1901623
Try unplugging the O2 and see what happens.
BTW I never found the cause of this, but I assume it was because of the MAFT-pro, because I swapped it out for lexus afm/550 mod and never experienced the problem again.

 

[3p141592654]

If you have TE1 jumpered and the throttle is closed (IDL signal 0V) and the car speed is 0 (stopped) then timing will be set to 10 degrees. If the timing is jumping around then the most likely scenario is the IDL signal is saying the throttle is open or your jumper is not making good contact. Fortunately it is easy to check. If all is good the MIL light will be blinking rapidly.

Also, on a seprate note if you have a Walbro installed, you need to remove the j-tube obstruction.

 

[Backlash2032]

J-tube bypassed. No codes, with the MIL blinking rapidly, so the IDL contacts in the TPS are closed, otherwise it would be giving a code 51, correct?

After PMing IJ. last night, he told me to check the CSI and circuit. I took that as there is probably a short to ground somewhere and the CSI could be just dumping fuel into the manifold. After about a half hour of struggling, I got the connector off of the CSI. And damn, I never knew how much of a difference that CSI could make with starting.. Anyway, after it started, I let it idle for awhile and it never really bogged out. The occasional miss, but every 7M i've heard has been like that. Took it for a drive around the block and no hiccups.. So I shut off the engine, popped the roof off, and it fired right back up with no problems. Took it for about an hour drive, including multiple stops, involving turning the engine off and letting it sit for awhile. Every time it fired right back up. So I decided to do a little pull. It pulled alright, but 3rd gear it started breaking up at 4k rpm. I'm thinking either spark plugs or CPS wiring..

 

[7M4EVR]

Hey backlash...if its not one thing its another with these bastard cars Lol...what is the condition of your injectors?

 

[Backlash2032]

They were advertised as freshly clean and flow tested.

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[7M4EVR]

Yeah I don't think that would explain the timing jump anyway...didn't u just do some sort of swap or do I have that mistaken?

 

[Backlash2032]

Yeah I swapped from my wrecked 90 to my new 89. Its running pretty damn good right now though. I think unhooking the csi actually fixed it.

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[jetjock]

That unplugging the CSI fixed it makes absolutely no sense at all.

 

[Backlash2032]

Well I'm sorry but it ran like a pile of crap before.. and now it runs pretty damn well.

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[jetjock]

If you say so. I say post hoc ergo propter hoc...

 

[Backlash2032]

Perhaps.. the only other thing I can think of would be CPS/CPS wiring, or the igniter

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[thevork]

Just a thought....hook the csi back up and see what happens.

 

[Backlash2032]

I want to but I'm gonna chance it atleast for now because I need the car for a couple days and that injector is a bitch to unplug lol

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