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Engine dying..

Cwazywazy

Cwazywazy

Single jingle
Joined
Aug 20, 2016
Location
Granby CT
I had the same exact problem with my old wagon where the engine would almost die or stall when i push the clutch in/rev it in neutral. I dunno how I fixed it, it just kinda went away after the rebuild in 2017. Now it's back. Somewhat related, sometimes under very light acceleration it'll just go dead rich and stay that way until I lift off or give it more gas. Sometimes it stalls when I'm trying to move off from a stop. Runs fine cold and progressively gets worse the further I drive.

I've tried:

boost leak testing, found one, fixed it, no real difference.
vacuum leak test, found none.
known good MAF, no difference.
dunno if good IAC, seemed to make no difference.
unplugging TPS, no difference.

<iframe width="560" height="315" src="https://www.youtube.com/embed/NmpdU-cd9IE" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 
Unplugging the o2 just made it run a tiny bit leaner. Once it's idling steady it stays idling fine, ac/fan kicking on and all.
 
^Tested that as well.

Pretty sure my idling down problem just requires a new IAC. I ran mine through the ultrasonic cleaner and it's way better but not fixed. Still no idea what's causing my other issue though. Definitely not the o2 sensor or the MAF, which are my usual culprits for these kinds of problems.

<iframe width="560" height="315" src="https://www.youtube.com/embed/hyjjVVtaVuI" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 
philski o'flood said:
it's almost always been that [CTS] sensor for poor running with me....
Click to expand...

Previous four Volvos I've bought, I replace FPR, CTS, CPS, sparks, wires, cap, rotor, timing belt-etc, water pump, belts, hoses, fuel filter, (whatever else I perceive that needs attention), and then I drive them.

In short, each one sat until this work was done, then I drive them. Recent 1990-240 I bought sat for about two months, and some $600.00 in parts were installed.

In OP's situation, he's got an old FPR, and rail pressure needs to be checked.
 
Dunno how to check without a test port and it's the only 3bar I have on there. Did check the vacuum line and that's fine.
 
I'm watching this thread.

I have a 1991 740 Turbo and intermittently I have a bog down issue where the engine fails to rev. When I stay in the throttle the revs will actually drop. I can usually get off the throttle and get back into it and the power will be back. I have an air leak I gotta fix and the wastegate puck is open (I gotta fab an actuator brack for the 16T). I will post back when I fix it. I've been busy fixing cars for pay.

Failure to rev is commonly lean fuel mixture or retarded ignition timing.
 
Cwazywazy said:
Dunno how to check...
Click to expand...

With a new FPR...if issue still exists....on return to tank side, insert a hose on FPR's return nipple, then place other end of hose into a bottle. With two people, one starts engine, while other sees if fuel flows into bottle....shut off engine when bottle 1/2 full.

Hence, no return flow to tank means not enough fuel pressure at rail

Notice - Do this with engine cold, and out in the open (not in a garage)....at your own risk, of course:-)
 
Another thing that happens to to the fuel pressure regulator is the diaphram inside gets too worn to move and regulate pressure. this makes the pressure too high causing stalling and strange operation. A good check of the pressure with a gauge will help figure that out if it's happening.
 
Cwazywazy said:
Shiny new FPR, exactly the same.
Click to expand...

Either timing is off, or not enough rail pressure...as noted

With a new FPR...if issue still exists....on return to tank side, insert a hose on FPR's return nipple, then place other end of hose into a bottle. With two people, one starts engine, while other sees if fuel flows into bottle....shut off engine when bottle 1/2 full.

Hence, no return flow to tank means not enough fuel pressure at rail

Notice - Do this with engine cold, and out in the open (not in a garage)....at your own risk, of course:-)
 
I can feel fuel running through the return line at idle. I did another boost leak test just to cover my bases and found the 4th injector seal is not sealing at all.. Dunno how I missed that the first time. Don't think that'd make it run rich, but hopefully that explains my idle problems.
 
Cwazywazy said:
...found the 4th injector seal is not sealing at all...
Click to expand...

Symptoms can point to various problems....like, "Runs fine cold and progressively gets worse the further I drive," suggests extra fuel enrichment in open loop (when cold) is without an issue, but when in closed loop comes the issue.

So, if injector seal on intake side was sucking air, yes, this will lean out mixture, with potential pre-denotation. If knocking happened, then LH will increase fuel ("it'll just go dead rich") and change timing (retard) to control knock.

>vacuum leak test, found none.

I assumed this was true....replacing an old FPR is about preventive maintenance.
 
I replaced the injector seals, did another leak test, and it's exactly the same. Also tried an unchipped ECU. It's not knocking at all. (Knocksense would light up if the knock sensor was seeing knock that isn't happening, so.)

I've ordered an OEM Bosch o2 sensor and ECU temp sensor, I kinda doubt those will fix my problem but I believe it needs a new o2 sensor anyway. Current temp sensor is almost new but it is a cheapo unit.

Right now it's doing the same thing in the last video but the idling down problem is much improved. Idle still dips and it'll almost stall, but the important thing is that it doesn't stall anymore when I come to a stop or take off. I still believe it just needs a new IAC. I found a cheapo China unit on eBay for 30 bucks.. Might be worth a try since I've already had 2 or 3 junkyard units fail on me.
 
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