Bernie

Hey Guys / Gals,

Since I put my car back on the road, it has developed a nagging little problem. This only happens when the engine is completely cold as in overnight and does not ever happen during the entire coarse of a day.

When I initially start the car up in the morning, it fires right up and then starts to stumble really bad. Then it will recover, rev up and then settle back to a normal idle.

It has gotten a little worse now in that it has actually started to stall from this stumble.. As soon as I fire it again, it lights right up and idles perfectly.

Just wondering if anyone else has encountered this particular problem before.

Regards
Bernie

jpitman2

sounds like extra air valve is not doing its job - if its L-jet? If its LH, maybe idle stabilizer , or temp sensor, which last is easiest to test....although they mostly fail the other way - start ok then go rich as they warm. check resistance across the sensor - 3k cold going down to 300 hot.
jp 83 Euro S AT 51k

AO

In my case it was coolant in the combustion chamber. You might want to pull the plugs and compare them... just in case.

Bernie

Its an 85 and I believe LH?
Willdo on the temp sensor and I was already contemplating it might be the idle stabilizer.
Other opinions are welcome.

Thanx for helping
Bernie

Big Dave

I had a similar issue....swapped in a good MAF (thanks Andrew!) and the problem is gone. I suspected the idle stablizer, too...but not any more.

Bernie

Will check on all things suggested guys thanx.
I doubt it is a headgasket problem since I am not losing any coolant. I went out and checked the level last night and it was still right at the centerline of the expansion tank - right where I set it.
I will keep an eye on it though in case it starts to drop.

I do have another round of repairs coming up shortly which will require removal of the intake again. Hopefully, I will have diagnosed what the problem is before I tear into it. That way, if something needs work under the intake, I can get to it as I do the other "leaky oil" fixes.

Cheers
Bernie

Bill Ball

One other variable. My car did this recently, while it is usually stone stable on start up. Stumbled a whole bunch backing out the driveway. After some playing with the throttle it stabilized. Next day, very similar instability. I also noticed but did not pay much attention to that the cold start-ups were not as brisk as usual - the starter turned more slowly, but not enough that I made much out of it. Finally, the car failed to start after a few days sitting, which was very odd. I charged the battery, which seemed to take surprisingly little time, and verified I did not have a parasitic drain. A couple of days later, almost dead battery again. Anyway, it was trying to tell me the battery was not developing the usual cold crank current anymore. I replaced the battery, which was 6 or 7 years old. All is back to normal.

anonymousagain

Bill - you mean very low rpm "catch it" with the throttle for 30secs or so, almost like no choke on a carbureter engine until it gets a little heat?

Have encountered this a couple times with SATA, on very cold mornings and had not been started for a few days. I was thinking maybe the relay was getting temperamental due to the lower than normal morning temp...hmmm may be battery slightly less than tip-top shape?....

Bernie

It could possibly be the battery getting old as it has a few miles on it...
The starter spins pretty freely though which I would assume it would struggle if the battery was the problem.

All good things to check though. I guess I will take it in and have it tested to see what its condition is.

Thanx for any and all help fellas.

Regards
Bernie

Bill Ball

In my case the starter spun slower than before, but the car started, although it developed the odd stumble when cold. The LH is so good at regulating idle, that when it is erratic, your mind ends up going through a lot of possibilities starting with the ISV, of course, but also including vacuum leaks, idle switch, MAF, LH itself, bad grounds, etc. The battery just isn't one of them, if the car starts.

In 89+ with the digital dash, a weak battery will often cause anomalies where the dash blanks out and the firmware code flashes during start-up if the current gets low. I wasn't seeing that, so I paid no attention to the battery despite the weird stumbling after start-up. I noted the slow starter turnover, but felt that could be a lot of things, including the starter, which is original. Finally the dash anomaly happened. I charged the battery. Then it happened again only a few days later despite verifying not having a parasitic drain (only 30ma flow). I knew that battery was toast. The charging system was working but was not adequate to have the car idle completely normal immediately after a cold start unless the battery was just off the charger. Anyway, the car starts a lot more briskly again and idles like its old self. The battery had been dragging for months, but I just didn't identify it.

Bernie - the GPZ750 Turbo must be a load of fun. I've ridden GPZ750s and thought they were VERY fast w/o the turbo.