Diagnose the issue anyone?

[erikv11]

Sorted this out on my 95 a couple weeks ago. Likely the forum figures it out more quickly than I did …

95 850 turbo
Car has intermittent engine stumble - some days it’s fine, others it will chug and skip here and there. Usually worse at startup. It’s annoying but while I’m ignoring the problem for about a month my solution is to only drive it when needed and only around town. Then I needed to make it my daily for a while so had to fix it.

What to do first?

[abscate]

Always start with ignition parts… cap ,,,,rotor ,,,,plugs,,,, wires

Then check for a Russet in the exhaust

[BlackBart]

Vacuum leaks. Those skinny turbo control vacuum lines.

[erikv11]

Vacuum leaks. Those skinny turbo control vacuum lines.

Vacuum leaks is why I hesitated to work on it, wasn’t looking forward to hunting them all down. Skinny turbo lines, maybe boost hoses? But this is where I started!

Most of the skinny lines are silicone but I checked as many as I could get to, all looked okay. Then I found a rubber nipple on the snorkel tube that crumbled in my fingers! But this didn’t fix it alas. The boost hoses are either silicone or recently replaced but I checked them all no joy. Starting fluid around the throttle body didn’t tell me anything. At this point I’m thinking okay maybe vacuum leak but on to other things.

[scot850]

+1 on the above, but also check fuel pressure and if a spare is available swap the fuel pump relay. Finally check the contacts on the IAC and MAF connectors. Both of those were causing a slight misfire on my friends 850 after getting it running as they were green and crusty.

Last thing is the crank sensor and the routing. A dealer mechanic re-route the cable on my 93 and got mis-firing, stumbles and cut-outs. The re-routing moved it too close to the distributor and the distributor firing caused the crank signal to disappear.

Neil.

[erikv11]

Always start with ignition parts… cap ,,,,rotor ,,,,plugs,,,, wires

Then check for a Russet in the exhaust

Arg! I went here second by mistake mostly because vacuum lines are easier to check. Checked one plug and the cap and rotor and all looked fine. Wires are recent but I didn’t test them. Kept looking at other stuff.

[abscate]

Car been sitting ? Zoo in the air filter ?

[erikv11]

+1 on the above, but also check fuel pressure and if a spare is available swap the fuel pump relay. Finally check the contacts on the IAC and MAF connectors. Both of those were causing a slight misfire on my friends 850 after getting it running as they were green and crusty.

Last thing is the crank sensor and the routing. A dealer mechanic re-route the cable on my 93 and got mis-firing, stumbles and cut-outs. The re-routing moved it too close to the distributor and the distributor firing caused the crank signal to disappear.

Neil.

I did check most of this stuff in like the third pass.

Did not reseat all connectors good idea, but checked the proximity of the coil wire to the CPS.
Tried running it without the MAF (go ahead and cringe abscate).
Swapped the fuel pump relay with a known good one.

None of that helped.

You guys are fast this is probably most (all?) of what I looked at.

Then like a week later after no progress with these checks and still limping around town the car got worse! At low rpms it really struggled but if I could get the revs up the engine was fine and didn’t stumble, however no power. Basically had revs but no boost. If I let the idle get low it would die, this was tricky around town but it’s a small town. Had to fix it at this point. Has to be vacuum?

[erikv11]

Car been sitting ? Zoo in the air filter ?

Car does not get used much over the winter/spring when this crept upon me and I did also check the air filter late at some point, another really good option it seemed. It was okay.

Along these lines I’m also thinking wiring damages of some kind maybe? Ugh.

[Chuck W]

Does it have good fuel pressure? (Didn't see mention of #'s for that)

Got a smoke tester you can borrow?