Driving down road engine cuts back, then OK
Thread Starter
Racer
Joined: Apr 2001
Posts: 302
Likes: 0
From: South Haven Michigan
Driving down road engine cuts back, then OK
I have a 90k mile, 1989 convertible. 3 times it has acted weird just driving down the road. I will be going along fine and then the engine cuts down by itself, there is no response at all if you hit the gas pedal, then it comes back on its own and is working fine.
- It does not run rough at all, it is there, gone and then comes back again, running smooth before and after the issue.
- The engine has not died during this issue.
- I believe all 3 times the car was under light acceleration, as in moving away from a light once and a stop sign twice.
- Twice it has lasted about a second, the other time maybe 4 seconds.
The manual says to start with the fuel filter, so that is what I did yesterday, and it did it again on the way home, so that didn't solve it. It has not set any codes so far.
This is what I have done so far:
- Fuel filter brand new (AC replacement) 8/18
Old one appeared fine, could easily blow through it
- Ohm test injectors, all from 16.5 to 17.0 ohms
- Fuel pressure test
Running 40 psi
Rev it up 45 psi
Shut off 40 psi
45 minutes later 29 psi
- Tapped MAF while engine running with a screwdriver, no issues
The mechanic said to clean the MAF, does this make sense? Does anyone have any ideas on what is wrong?
Thanks for any help you can give me.
- It does not run rough at all, it is there, gone and then comes back again, running smooth before and after the issue.
- The engine has not died during this issue.
- I believe all 3 times the car was under light acceleration, as in moving away from a light once and a stop sign twice.
- Twice it has lasted about a second, the other time maybe 4 seconds.
The manual says to start with the fuel filter, so that is what I did yesterday, and it did it again on the way home, so that didn't solve it. It has not set any codes so far.
This is what I have done so far:
- Fuel filter brand new (AC replacement) 8/18
Old one appeared fine, could easily blow through it
- Ohm test injectors, all from 16.5 to 17.0 ohms
- Fuel pressure test
Running 40 psi
Rev it up 45 psi
Shut off 40 psi
45 minutes later 29 psi
- Tapped MAF while engine running with a screwdriver, no issues
The mechanic said to clean the MAF, does this make sense? Does anyone have any ideas on what is wrong?
Thanks for any help you can give me.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
There are some horror stories on this fourm about the problematic OEM multechs that were installed '89s and the surrounding years. A great number of people have swapped their stock Multechs (non ethenol compliant)in for a set of Bosh III (ethenol compliant)....myself included.
Things to check (other than the fuel injectors):
Fuel pressure regulator diaphram leaking.
The wire to the O2 sensor...make sure it isn't grounding to the exaust or heat shields while driving.
Things to check (other than the fuel injectors):
Fuel pressure regulator diaphram leaking.
The wire to the O2 sensor...make sure it isn't grounding to the exaust or heat shields while driving.
Thread Starter
Racer
Joined: Apr 2001
Posts: 302
Likes: 0
From: South Haven Michigan
Thanks for chiming in, answers below.
The tank was full the first time, 1/2 full the second time, 1/4 full the third time.
The ohm test was cold. The injectors are 3 years old, but only about 1200 miles on them.
It does not run rough or miss when this happens, it is like someone shut it off completely, then it comes back. But the engine never dies.
Wouldn't I see the pressure drop off faster if the regulator diapragm was leaking? It is still 29 psi after 45 minutes of sitting.
No smell of gas when this happens. Car starts fine.
It has not set any codes so far.
The tank was full the first time, 1/2 full the second time, 1/4 full the third time.
The ohm test was cold. The injectors are 3 years old, but only about 1200 miles on them.
It does not run rough or miss when this happens, it is like someone shut it off completely, then it comes back. But the engine never dies.
Wouldn't I see the pressure drop off faster if the regulator diapragm was leaking? It is still 29 psi after 45 minutes of sitting.
No smell of gas when this happens. Car starts fine.
It has not set any codes so far.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
Ignition module or coil would be my first guess for a quick cut off then on. Overheats cuts out cools of and runs again. If not that a bad connector somewhere and sure hope not that could be a long search..
Thread Starter
Racer
Joined: Apr 2001
Posts: 302
Likes: 0
From: South Haven Michigan
Thanks ddahlgren.
I am leaning electrical as well. The first time it did this I had just left my garage and had just pulled out onto the main road, so the car was not even warm yet. The second time, which was the worst, about 3-4 seconds, it was completely warmed up. The third time was just about completely warmed up.
I also fear a loose connector somewhere, could be anything anywhere then.
I am leaning electrical as well. The first time it did this I had just left my garage and had just pulled out onto the main road, so the car was not even warm yet. The second time, which was the worst, about 3-4 seconds, it was completely warmed up. The third time was just about completely warmed up.
I also fear a loose connector somewhere, could be anything anywhere then.
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Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
Has anyone done anything before this happened in at least recent past under 500 miles ago? if so start there or at least in that area.. Fixed radio heater anything under the dash or engine compartment? I know the engine dying is very distracting but if all possible see if you can notice anything else not working.. May be on a common circuit or ground wire. See if something magically goes on light anything that would also be a ground wire somewhere. Open hood start car and start wiggling wires and see if you can make it fail.. On an L98 there is a pigtail on the distributor that you can not see easily with the cap on. Mine was rubbing the firewall and put some of that black plastic covering on it like the rest of the car has. If that shorts the car will stop.. It wouldn't hurt to check the connectors for the distributor coil ign module etc. Hit them with some contact cleaner and make sure the pins have plenty of tension. You want them stiff enough so it is a tiny struggle to put them together. That has fixed dozens of things on my car.. If all else fails start cleaning ground wires they are buryed everywhere sorry to say..
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Joined: Dec 1999
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From: Almost all Skyline Cruises Vettes at Waterside 1-5
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Safety Car
Joined: Jan 2008
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From: Vero Beach Florida
There are 2 MAF relays one controls normal MAF signals the other controls burn off. I believe burn off happens after you turn off car, the wire in MAF is super heated to remove any residue.
Race Director
Joined: Dec 1999
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From: Almost all Skyline Cruises Vettes at Waterside 1-5
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The burn off relay is generally not the prpblem, it is the signal relayBe sure though to replace both relays at same time...per Gorden K, replacing one creates overload and burns one up
Have you checked for codes? This condition should throw codes
be careful spraying anything into MAF and don't spray anythimh with solocone in it
Thread Starter
Racer
Joined: Apr 2001
Posts: 302
Likes: 0
From: South Haven Michigan
Thanks for the input. It hasn't set any codes so far. I thought I would raplace both MAF relays while I was at it. I didn't want to spray anthing on the MAF because I believe I read on on this board quite a while ago that it wasn't a good thing.
Intermediate
Joined: Aug 2009
Posts: 25
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From: Joliet IL
Mark, I am having the same issue with my 93. Runs great for about 20 minutes, or until it warms up, then stumbles, at first it never stalled but has progressively gotten worse. I'm not throwing an codes either, checked the ICM & I've already been through the fuel and vacuum systems, replaced the EGR, etc.but not the coil. I bought a new factory coil today and will install tomorrow and let you know what happens. But my symptoms sound exactly like yours.
Heel & Toe
Joined: Sep 2009
Posts: 16
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Responce and Question?
I had the exact same symptoms with my 96. Would be running fine and all of a sudden I would lose all power. Once or twice it stalled, but would start right back up. Turned out to be the alternator needed a rebuild! It hasn't acted like that since.
Now I have another problem. Very random, no power whatsoever. Turn the key, nothing, no lights, no cranking, nothing. Got out, opened hood. Looked for something obvious, loose battery cable, corrosion. Shut hood, and started right up and ran fine. I'm thinking maybe bad ground. Any other ideas, anyone?
Oh, and thanks ahead, new here, loads of good info and knowledge!
Now I have another problem. Very random, no power whatsoever. Turn the key, nothing, no lights, no cranking, nothing. Got out, opened hood. Looked for something obvious, loose battery cable, corrosion. Shut hood, and started right up and ran fine. I'm thinking maybe bad ground. Any other ideas, anyone?
Oh, and thanks ahead, new here, loads of good info and knowledge!