Engine dying in reverse?

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Idontlikereverse
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Engine dying in reverse?

Post by Idontlikereverse »

Last summer I bought a 1979 633csiA. It had minor issues and wasn’t happy in reverse or at idle, but it made the 4000 kilometre journey back from Saskatoon to Halifax Nova Scotia with only a fuel line coming undone on the way. Since then ive done regular maintenance, but I noticed that after checking for compression it now dies in reverse. Once the car is warm it idles fine, but as it starts it needs gas in order to stay alive. I don’t know if this is a part of the reverse issue. I’ve jacked the car up to see if it would still die if there was no load on the tires and it still did. It seems like it’s stalling. If I give it gas while or just after putting it into reverse it still dies. I hope it isn’t a transmission issue... has anyone else dealt with this?
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Ralph in Socal
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Re: Engine dying in reverse?

Post by Ralph in Socal »

I would check for a fuel supply issue. Make sure pressure is not dropping far below about 45psi. Also check fuel volume by measuring the fuel discharged through the pressure regulator outlet. You should get about 3 liters (from my faulty memory) during one minute of collection.

Ralph
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Pod
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Re: Engine dying in reverse?

Post by Pod »

I was thinking the same as Ralph! Sounds as though you may have a blockage or poorly performing pump.
Last edited by Pod on Mon Jun 10, 2019 4:12 pm, edited 1 time in total.
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Idontlikereverse
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Re: Engine dying in reverse?

Post by Idontlikereverse »

Thanks guys I’ll definitely give those a try I think you guys are right about it being a fuel delivery issue. I fixed its other problems and took it for a spin where I was trying to see if it would reverse at all, and it would sort of reverse for a few meters very jerk-ily if I was at about half throttle, but it would sound like it’s getting no gas and then eventually it would cut out and die. I have a feeling you guys are right. I can’t understand why this would only be a problem in reverse though, I lack a lot of knowledge when it comes to auto transmissions and fuel injection.
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86_6series
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Re: Engine dying in reverse?

Post by 86_6series »

So this stalling in reverse happened after a compression test.

Is it an auto tranny?

I can't think of any link between compression test and a reverse problem.

All I come up with is could be the neutral safety switch wires move

when shifting into reverse to cut out ign.

Just my $.02
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Pod
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Re: Engine dying in reverse?

Post by Pod »

Idontlikereverse wrote: Mon Jun 10, 2019 1:04 pm I can’t understand why this would only be a problem in reverse though
Maybe because in reverse you don't rev the engine, but let it go back either at tickover or low revs? Does it drive forward @ tickover without the same problems?
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Idontlikereverse
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Re: Engine dying in reverse?

Post by Idontlikereverse »

I realize I never posted the solution - it was a crack in a Mass air flow hose.

This problem was super frustrating and the crack was only visible from below. Hopefully this will help someone one day.
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RossDinan6
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Re: Engine dying in reverse?

Post by RossDinan6 »

Not that I have an early car, Motronic or an auto, I am a bit curious. My thinking is there should be little or no difference in engine load in drive or reverse. why'd it stall in reverse and not in drive. The air flow/leak should be the same.

Inquiring minds want to know :D
Ross
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86_6series
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Re: Engine dying in reverse?

Post by 86_6series »

First--thanks for posting the solution.

After reading this I have the same question as RossDinan6.

Could the crack open wider with the engine torqueing in reverse?
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Idontlikereverse
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Re: Engine dying in reverse?

Post by Idontlikereverse »

I think In hindsight it did occasionally die in drive. I guess there may be more load on the engine in reverse causing it to sputter and die. I remember the idle to be quite high in park and then in drive it would go down to about 6-700 rpm. Maybe when in reverse it would go too low and die.

One time I put it in reverse and floored it right away. If I remember correctly it started lurching just like when you are running out of fuel.

I’m fairly unsure though, it has been a little while and the exact details have escaped me.

This is the part I am referring to having a crack - the tube leading to the maf.
34EDD64D-E4FE-48B3-8343-28CB5F6920B8.jpeg
34EDD64D-E4FE-48B3-8343-28CB5F6920B8.jpeg (510.08 KiB) Viewed 2587 times
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marc79euro645
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Re: Engine dying in reverse?

Post by marc79euro645 »

I hate to say it, but, that hose crack should not have had any affect on idle, or running, as it's ahead of the afm. Glad to hear it's working though!
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Idontlikereverse
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Re: Engine dying in reverse?

Post by Idontlikereverse »

That’s another thing that never made sense to me.

I took it to a euro shop who found the crack and replaced it. Everything ran perfectly after that. I didn’t think it should have made a difference either, but other people said it can cause it to run lean?

I’ve heard of aftermarket cold air intakes failing and causing a rough idle but I’m not sure why that’s the case.

I hope the car is still running fine :D , but it has since replaced with a bigger project 635.
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RossDinan6
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Re: Engine dying in reverse?

Post by RossDinan6 »

The ECU can not tell if there is a leak anywhere from the air filter inlet to the AFM. Anything after the AFM will be noticed, this is unmetered air. Try pulling your dipstick that will introduce unmetered air as well.

I suspect they found something minor, or accidentally fixed it without knowing it.
Ross
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