1990 ZF6 - Cold 1st Launch Issues
Thread Starter
Cruising
Joined: Jun 2021
Posts: 13
Likes: 9
From: Lenexa, KS
1990 ZF6 - Cold 1st Launch Issues
I have a 1990 with the ZF6 transmission and have been experiencing an odd issue that I am hoping you all could maybe help me out with. I will do my best to explain the issue:
After the car has been sitting over night and cold I can back out of the driveway just fine but when I try to take off in 1st gear I am having to give it a lot of gas to avoid stalling upon launch. I can have 1500-2000 RPMs and begin to release the clutch and it will drop to 500 RPMs.
The first two take offs are rough. Once I have driven around for a very short period of time I experience zero issues taking off in 1st gear. Not much gas needed, smooth take off, etc.
Any thoughts? Thanks in advance.
After the car has been sitting over night and cold I can back out of the driveway just fine but when I try to take off in 1st gear I am having to give it a lot of gas to avoid stalling upon launch. I can have 1500-2000 RPMs and begin to release the clutch and it will drop to 500 RPMs.
The first two take offs are rough. Once I have driven around for a very short period of time I experience zero issues taking off in 1st gear. Not much gas needed, smooth take off, etc.
Any thoughts? Thanks in advance.
Safety Car
Joined: Sep 2001
Posts: 4,154
Likes: 553
From: Glenbeulah Wi
Car is in open loop and probably lean, which means it will be very easy to stall. Check the basics like fuel pressure and timing, also see if you can get a scanner to see what the engine coolant temperature sender is reading, if it is incorrect it could be the issue. You could also have issue with your injectors but before we start guessing check those few items and report back.
Thread Starter
Cruising
Joined: Jun 2021
Posts: 13
Likes: 9
From: Lenexa, KS
I will check fuel pressure. I have yet to replace anything on the fuel sending unit.
I took the top end apart a while back and did take the distributor out. Could be timing related. I will check that out. Injectors were recently replaced with Bosch III's.
I appreciate the quick reply!
I took the top end apart a while back and did take the distributor out. Could be timing related. I will check that out. Injectors were recently replaced with Bosch III's.
I appreciate the quick reply!
Pro
Joined: Aug 2021
Posts: 503
Likes: 33
From: S Fla
What does your digital water temp say when it starts working correctly? Do you immediately start backing up after you start it, or do you let it run for more than a few seconds? I could easily be wrong, and someone more experienced will undoubtedly drop in, but here's a possiblity. If it's warmed up by the time it starts working correctly you could have an IAC getting flaky. The reason I asked about backing immediately is because I have a feeling that during the first few seconds of run time the car may still be trying to correctly set the IAC, so that could be a period of time to disregard for this particular situation.
Among the same lines, maybe a vacuum line has developed a crack that is less noticable after the car has warmed up.
Among the same lines, maybe a vacuum line has developed a crack that is less noticable after the car has warmed up.
Thread Starter
Cruising
Joined: Jun 2021
Posts: 13
Likes: 9
From: Lenexa, KS
I will check water temp.
I immediately start backing up after starting. I replaced the IAC a few months ago (albeit with a cheap replacement) due to stalls occurring at idle, which hasn't happened in a while.
Could definitely be a vacuum issue.
Diagnosing the root cause is half the fun... right?
I immediately start backing up after starting. I replaced the IAC a few months ago (albeit with a cheap replacement) due to stalls occurring at idle, which hasn't happened in a while.
Could definitely be a vacuum issue.
Diagnosing the root cause is half the fun... right?
Thread Starter
Cruising
Joined: Jun 2021
Posts: 13
Likes: 9
From: Lenexa, KS
You know what... this just made me recall something that I noticed when I started the car the other day. The fan came on immediately which I thought was odd. Didn't think much of it as it shut off shortly thereafter. Probably going to order a coolant temp sensor.
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Safety Car
Joined: Sep 2001
Posts: 4,154
Likes: 553
From: Glenbeulah Wi
Thread Starter
Cruising
Joined: Jun 2021
Posts: 13
Likes: 9
From: Lenexa, KS
I believe it may have occurred prior to the switch. It sounds silly but I'm honestly not 100% sure. I haven't had much time with the car to understand normal vs. not normal.
I had a coolant leak that lead to a top end tear down to replace intake gaskets. I did injectors, EGR valve, tstat, coil, fuel pressure regulator, plugs and wires while I was at it.
I had a coolant leak that lead to a top end tear down to replace intake gaskets. I did injectors, EGR valve, tstat, coil, fuel pressure regulator, plugs and wires while I was at it.
Racer
Joined: Apr 2013
Posts: 435
Likes: 4
From: Guilford NY
I have a 1990 with the ZF6 transmission and have been experiencing an odd issue that I am hoping you all could maybe help me out with. I will do my best to explain the issue:
After the car has been sitting over night and cold I can back out of the driveway just fine but when I try to take off in 1st gear I am having to give it a lot of gas to avoid stalling upon launch. I can have 1500-2000 RPMs and begin to release the clutch and it will drop to 500 RPMs.
The first two take offs are rough. Once I have driven around for a very short period of time I experience zero issues taking off in 1st gear. Not much gas needed, smooth take off, etc.
Any thoughts? Thanks in advance.
After the car has been sitting over night and cold I can back out of the driveway just fine but when I try to take off in 1st gear I am having to give it a lot of gas to avoid stalling upon launch. I can have 1500-2000 RPMs and begin to release the clutch and it will drop to 500 RPMs.
The first two take offs are rough. Once I have driven around for a very short period of time I experience zero issues taking off in 1st gear. Not much gas needed, smooth take off, etc.
Any thoughts? Thanks in advance.
Good luck.
Pro
Joined: Aug 2021
Posts: 503
Likes: 33
From: S Fla
Hey, MikeT. If I read that right, that your clutch only disengages near the very bottom of it's travel, you should probably find out why and fix it. I was talking with ZFDoc about things to check on a zf car, and that was one of his top things he told me watch out for. He said that the clutch should not engage near the top or bottom of it's travel because of issues with incomplete clutch engagement/disengagement, resulting in bad synchros, leading to a multi-thousand dollar rebuild.
Racer
Joined: Apr 2013
Posts: 435
Likes: 4
From: Guilford NY
Hey, MikeT. If I read that right, that your clutch only disengages near the very bottom of it's travel, you should probably find out why and fix it. I was talking with ZFDoc about things to check on a zf car, and that was one of his top things he told me watch out for. He said that the clutch should not engage near the top or bottom of it's travel because of issues with incomplete clutch engagement/disengagement, resulting in bad synchros, leading to a multi-thousand dollar rebuild.
Can it be adjusted?
Pro
Joined: Aug 2021
Posts: 503
Likes: 33
From: S Fla
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
It is for some....not so much for others. IMO/Experience, the fastest, cheapest, easiest way (my favorite way) to bleed it is to fill the reservoir "enough", the just tap the pedal ~1" or so down and let it come back quick a bunch of times. Every 20 or so taps, I'll make a full stroke, to help move air bubbles up toward the master, and also to assess the pedal feel. That method should take <5 minutes. I some times open the driver's door, squat near it's hinge and use my right hand "tap" the clutch pedal as I can do it faster w/my hand than my foot.