76FJ55

My MY85 auto is way down on power after I did a bunch of work on it. A lot has transpired with it lately so I will list everything I know and have done. And the car ran well before all this.

It started with a radiator leak, which I'm sure, is unrelated to my current problem, but initiated this long chain of events. So I had a second radiator to install which meant I was disassembling the area at the front of the motor, and I also had a new timing belt on the shelf, so I thought I'd do that at the same time... I'll go to list form from here:

Non leaking radiator
New Thermostat and seals
New TB
New TB gears (timed with 32V'r)
New PS lines
New fuel lines
55psi FPR (MY87)
Porken's LH55 chip
PorKen's updated EZF chip
X-pipe
New O2 sensor
Air pump delete
Cleaned MAF
New air filter

I have two parts that I am initially suspect of the MAF and LH.
The MAF simply because it appears to be original, I had it out and sprayed lots of cleaner at it.
And the LH computer: Most likely and self induced. When I went to reassemble the LH I miss read the circuit board and installed the chip backwards. The car of course did not start. I realized my mistake and flipped the chip around to its correct orientation. Afterward the car still failed to start. I notified Ken, and he graciously sent me a replacement chip (thanks Ken). Apparently I am not the first to have installed a chip backwards, and was told that doing so erases the programming when the unit is powered up. I received my new chip, installed it and the car fired right up (disaster averted, or so I thought), however the car still doesn't run right, so I am suspecting that I managed to damage the LH unit itself in the process.

Symptoms:
Starts well hot or cold
Idles reasonably well, just slightly rough, nothing I'd be concerned with if it weren't for the lack of power.
First morning I drove it (it was still cold out) engine still cold, popped back through the intake on anything more than light throttle.
Once engine was warm it got significantly better, but was still noticably down on power, and I was driving very easy that day as I had just gotten it all back together.
Day 2 popped back through the intake on accel. with engine cold.
Never got the engine warm, as I had an unfortunate run in with a Toyota pick-up…

New fender later and now it is warm out, car’s back on the road, and WAY under powered. So I have started running diagnostics. Here is what I’ve found this far.

Temp II checks good at the sensor and at LH, EZF,
Air temp sensor tests good at sensor and EZF,
Fuel pressure good
Timing appears good _10 at idle goes to ~45 when rev’ed (MAP connected) and to ~20 (MAP disconnected)
WOT switch good at LH, EZF
Idle switch good at LH, EZF
Resistance through hot wire checked good at LH

Anything else I should check before looking for a LH and MAF?

Anyone with a spare 85-86.5 LH?
One test option would be to try my LH in someone else’s car, but it would require access to another 85-86.5 setup with a 55psi reg., and I don’t know of any locally. Is there anyway to test the
LH other than a functional test?

As always, all help and suggestions are greatly appreciated.

Simon

dprantl

What about a vacuum leak? Are you sure you didn't knock a hose loose during all the work? Did you cap the line for the diverter valve when you removed the air pump?

Dan
'91 928GT S/C 475hp/460lb.ft

Mongo

Also, have you had the CO percentage adjusted on this new MAF?? That may also clear up a little bit of the running issue also.

Bill Ball

Are you sure the 87 FPR is giving you the right FP? Might it have a diaphragm leak (check for gas in the vacuum line)? You could put the original chips back in and test the LH in another 85/6. There's not much else you can do to evaluate the LH.

sendarius

"Popped back through the intake".

Are you SURE you have all the plug leads on right?

Bart-Jan

Since you've installed a new timing belt, could it be that one of the cams is one tooth out? I've had the same symptoms on another car and this appeared to be the reason...

SteveG

Along this line, where did you set the cams? It would seem if you were using the tool, there would be no tooth issue as you must have turned the engine several times, but perhaps a "+" or "-" was misapplied.

ROG100

Simon,
I have a spare MAF and LH for your car - let me know and I can ship them today.
Roger

76FJ55

A vacuum leak is a possibility, and I will investigate further this evening/weekend. I did plug the line that originally went to the diverter valve so that isn't it but as you say I could have knocked something else loose while I was in there. I would think a va leak would affect idle more so than full power which seems to be the oposite of my symptoms, but it is still something to look into. one thing I did notice while changing the fender was that the lines to the carbon canister where in rough shape so that could be a possible leak source.
I'm still running the original MAF. I cleaned it with MAF spray cleaner, while I had it out, but made no changes to it otherwise. So unless I damaged it while spray cleaning it seems that It shouldn't cause such a significant problem. I'll try setting the idle mixture per PorKen's thread here and see if it helps.
I check the fuel pressure per the 87 section of the manual. Had 58psi engine off and relay pumped. And had 47psi engine at idle and fuel pressure responded to throttle position throttle changes, so I’m confident it’s not a FPR issue.
The plug wires were not touched during this round of maintenance, and I’m sure they are correct. The car ran well before this.
Back firing through the intake makes me think it is excessively lean, or at least this is a common indicator of a lean condition on the motorcycles I’ve worked on. This was what drove my to suspect the FPR initially but fuel pressure has tested good.
In an effort to get it running I set the cams at 0 degrees as per factory and figured I’d play with the timing after I got a better feel for how the new chips and X performed, as you can tell I haven’t made it to that stage yet so they are both at 0 which should eliminate any + - confusion errors.
I’ll be back at it this evening and over the weekend. I’ll keep checking back here for Ideas, and to update with any progress.

76FJ55

Awesome, your the best. I'll send you an email. If your shipping stuff there are a couple other minor items I can use.

PorKen

Popping through the intake is usually running too lean.

I think it's very unlikely to be the ECU. Most likely the MAF is toast, or you have the wrong FPR.

Try swapping in someone else's MAF (85-95 all the same).

Bosch FPR should be stamped: 0 280 160 262

dr bob

Check the cam timing, then double-check the cam timing. Missing by a tooth is causing the exact same symptoms on James' '85 Euro you cite. Idles OK but rough, gets worse as power demand increases.

Mongo

You cleaned it with spray cleaner??? I lost a MAF to that stuff. A previous mechanic had used it and didn't let it dry long enough. MAF failed as soon as the car started. Gotta be careful with that stuff. Although I can't say I had any trouble cleaning the second MAF with it and letting it sit for a couple hours to dry.

PorKen

After some coffee, I see that you checked the fuel pressure, so it's the correct FPR.

MAF or cam timing.

Did you spin the engine with the starter, and recheck the timing after adjusting?

76FJ55

I'd driven the car prior (days prior so cam timing was done on cold engine) to verifying the cam timing with the 32V'r, so I'm confident both cams are set to 0 deg. So it looks like opinions are leaning towards the MAF. Roger should be sending me a spare MAF and LH soon, so I'll try the MAF first and see how it goes. In the mean time when I get home I'll pull my MAF for a closer inspection.