• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

940 Rough idle, fuel pressure issue?

I took apart the timing covers to make sure the timing was right, all is well. Disconnected my boost controller and ran on WG pressure to make sure that's not a vacuum leak, that's fine. I drove the car earlier, and it accelerates okay except for an occasional hiccup like it started doing last week.
What I noticed and forgot to mention, it's been really sluggish to get going from a stop. The car has NO power, like it's starting in 2nd gear. After a few seconds, it picks up and revs normally, but it's really awful from a stop. Especially with the AC running (as expected)!
I don't think this is an issue of timing, being that this problem began prior to installing this head/cam.

I checked the fuel pressure with the vacuum hose disconnected, but my junk gauge decided to stop working and hold the highest pressure. Interesting, it doesn't have a check valve. I saw 35 PSI, but I don't know if it was fluctuating at all.

I also swapped in a spare power stage, no difference.
 
I haven’t actually figured that out yet... it doesn’t make much sense. The head gasket looked fine, valves look fine, and the piston doesn’t have any obvious issues. No excessive movement from what I can tell. They all 4 move a little bit at TDC, but I assume that’s normal being that all 4 do it. And it’s not a ton of movement at all.
I’m thinking it’s the fuel pump (causing the idle and acceleration issues, not the low compression). Gonna start with the in-tank pump.

I will go ahead and do another compression test though, because I’m really curious as to what it will show now with the new head.
 
bmdubya1198 said:
I haven’t actually figured that out yet... it doesn’t make much sense. The head gasket looked fine, valves look fine, and the piston doesn’t have any obvious issues. No excessive movement from what I can tell. They all 4 move a little bit at TDC, but I assume that’s normal being that all 4 do it. And it’s not a ton of movement at all.
I’m thinking it’s the fuel pump (causing the idle and acceleration issues, not the low compression). Gonna start with the in-tank pump.

I will go ahead and do another compression test though, because I’m really curious as to what it will show now with the new head.
Click to expand...

lots of information on this forum... just a matter of communicating with the correct person/s

:-P
 
Last edited:
Yup, I'll check today. I'm hoping to see better numbers than before, but we shall see!

Oh yeah, there's a ton of info, it's just a matter of using the right wording to search, as well as talking to the right people. Unfortunately this forum isn't as active as it used to be.
 
This sounds a bit like there may be compounding problems:

1) The compression in #1 relative to the others is no good. It doesn't seem to fit as a cause of your symptoms, however.

2) If your fuel pump primes to only 20 lbs and bleeds off to zero after 30-45 seconds, that sounds to me like a bad fuel pump check valve, leaky injectors, and perhaps(?) a bad main pump.

When you say it has no power off idle and then clears up, does it have no power "smoothly", or is it like a misfire?

How about I armchair QB this thing and say you have a bad #1 injector that's washing the cylinder. When you run your compression test, the cylinder walls are clean and it's reading lower. It would explain the fuel pressure readings, and the crap running.

But hey, I'm 1000 miles from you. What do I know?

Is there any funny business about this car/engine that might help?
 
Nothing odd that I know of. Your theory makes sense though. Like I said, I’m gonna do another test today and see if the low compression still exists.

It’s smooth, but I also have a “hiccup” that occasionally happens on acceleration once I’m already driving. It’ll start off real sluggish, then pick up power and it feels fine. Then if I punch it while moving, it’ll feel like a misfire and then pick right back up.
 
Compression tested it cold today... pretty much the same numbers as before. Looks like the compression issue is probably ring-related, as I originally suspected. Oh well!

Compression numbers were
1- 112
2- 154
3- 157
4- 162

As for the rough idle, I'm thinking replacing both of the fuel pumps should take care of the rough idle and hesitation. Low pressure pump is on the way, I'll probably go ahead and order a main pump shortly.
 
Plugs look pretty good too, surprisingly. These are brand new BKR7ES.
M2W2Xzx.jpg
 
I would be interested to see RUNNING COMPRESSION numbers.

It kinda sounds like you are misfiring. I would make sure a good cap and rotor are on there. And good plug wires that are snapped onto the plug well. I recommend BOUGICORD wires.

You could also do a CYLINDER DROP TEST. Unplug an injector one at at time and see if the idle changes. If no change, you found the hole with the problem.
 
I’ll have to try a running compression test.

I tried that, idle dropped about the same when I unplugged each injector. No worse with #1 unplugged than any other cylinder.

Cap and rotor are definitely good though, I just swapped a brand new cap on with no difference. The old Bosch one doesn’t look bad either. Wires are STI rather than Bougicord, but I’ve used them before and they’re pretty good quality. I get a nice solid click onto the plugs and the cap.
I’ve also tried multiple ignition coils with no perceivable difference.
 
Otto Mattik said:
Have you diagnosed, or swapped #1 injector to another cylinder for a comparison ?

;-)
Click to expand...

I'm PRETTY sure I kept them in order when I swapped the rail, but I honestly don't remember. If not, that will be my next step.
Main fuel pump came in this morning, so I'll swap that out today. Lift pump will be here tomorrow. Between the two, I'm hoping that will at least fix my low power issue, if not my rough idle that started this whole thread.
 
I replaced both fuel pumps, as well as the sock and check valve today, and it runs exactly the same. I finally drove it around for an extended period of time, and it doesn't really have any issues in the higher end, but accelerating from a stop is where it stumbles and is a real slouch.

Any other ideas? I swapped over a spare MAF sensor and that made no difference either. I think the only thing I haven't cleaned/checked/replaced is the O2 sensor, and I don't know that it could cause that much of a problem.

Maybe the throttle switch? Does that do anything beyond sending idle/WOT signals to the ECU? It clicks as it should when opening the throttle.
 
A few issues I've had with 240's

a) faulty connections/corrosion/grounds/vacuum leaks
b) faulty FSR(Fuel pump relay)
c) failing/ed Power Stage
d) failing/ed fuel pump/s
e) distributor cap internal crack(not visible)
f) faulty plug wires
g) plugged cat
h) bad/old fuel or failed coil(cars in non-ideal storage conditions)
i) bad IAV/IAVC on a 2.2 caused a high idle

Did you diagnose a possible leaky injector scenario, swap or injector flow test ?


:cheers:
 
Last edited:
Otto Mattik said:
A few issues I've had with 240's

a) faulty connections/corrosion/grounds/vacuum leaks
b) faulty FSR(Fuel pump relay)
c) failing/ed Power Stage
d) failing/ed fuel pump/s
e) distributor cap internal crack(not visible)
f) faulty plug wires
g) plugged cat
h) bad/old fuel or failed coil(cars in non-ideal storage conditions)
i) bad IAV/IAVC on a 2.2 caused a high idle

Did you diagnose a possible leaky injector scenario, swap or injector flow test ?


:cheers:
Click to expand...

I can't rule out a plugged up cat, but I'm getting plenty of exhaust out of the back just from putting my hand there.
I swapped over a spare power stage, no difference.
I can pull out the idle air again, but I cleaned it when I got the car and was initially trying to diagnose this issue. I might try to swap over a spare ignition coil.

It's really weird though, because although the rough idle has been here since I bought it, there was never a problem with hesitation otherwise. And like I said, once I get moving, it runs fine. The boost gauge is steady and it has no problem revving out to 6k RPM. It's only in the low end that it "hiccups" once it finally gets moving.

I have not swapped the injector/s yet, but I may go ahead and swap my spare blues in today. Either that or grab a set of green tops currently sitting at the junkyard.
 
Swapped out the injectors for another set of green tops, no difference at all. The hesitation is still there. Ugh... this is getting annoying!

Could the neutral safety switch cause any problems? I'm just thinking, since my friend pointed out last week that my reverse lights didn't work. After checking the fuse and probing the reverse light bulbs, I believe the neutral safety switch has failed. IIRC, it provides a signal to the ECU to raise the idle in P and N.
 
Last edited:
You must log in or register to reply here.
Back
Top