940 with wierd idle, low rpm stutter, stalls and misfire

[FMM]

Hey
I have a slightly modded volvo 940 which i have been working on for a little over a year and finaly got it on the road, however over the time that i worked on it an issue with the idle came up, it bounces around 650-850 rpm and it stutters when doing so, and it also misfires quite often in idle.

When driving it doesnt like low rpm at all, it jerks and misfires quite alot but it seems to be only when im going below 70-ish km/h and its only when coasting, if i floor it all the issues go away

Sometimes when pressing down the clutch after driving it will dip quite low in rpm and sometimes stall but it seems to be at random meaning other times the rpm wont dip at all.

Here the other day it had trouble starting i had to press down on the gas to start it, but its always a little slow to fire up

I bought the car modded and here is what was done to the car when i got it:

-A holset hx35 was fitted
-AMM was relocated to just before the TB
-unkown injectors
-another camshaft and they adjusted the timing a little bit
-EGR delete

i made some changes to the car myself and i worry that i have messed something up because if my memory is correct then the issue came somewhere along the mods i have done

-Bosch 968 injectors and ignition/fuel chips to match
-walboro fuel pump
-multigauge with rpm gauge, for the rpm gauge i get the signal from the ignition control module(some of my suspicions are on that)
-adjustable fuel regulator

Im forgetting some stuff, but its been bugging me for some time now and i cant tell anymore if the cause is just the camshaft being adjusted.

Anyway let me know what you think

 

[MistrThou]

A few things I'd consider:
Do you have any pressure/vacuum leaks in the hoses, intake gasket, injector seals, TB etc...?
I've had some similar issues with leaky intake manifold. It did NOT like idling (where smallest amounts if air leaks can interfere with low engine speeds).
Another, I've heard mixed reviews of placing the AMM in boost. On the stock turbo cars, they are on the suck-side of the turbo. That's where I placed mine when I +T'd a 240.

Does the idle change at all if the AMM is disconnected?
Once you get into adjustable fuel regulators, maybe you'd want a wideband O2 sensor and gauge to see where the AFR is.

 

[FMM]

A few things I'd consider:
Do you have any pressure/vacuum leaks in the hoses, intake gasket, injector seals, TB etc...?
I've had some similar issues with leaky intake manifold. It did NOT like idling (where smallest amounts if air leaks can interfere with low engine speeds).
Another, I've heard mixed reviews of placing the AMM in boost. On the stock turbo cars, they are on the suck-side of the turbo. That's where I placed mine when I +T'd a 240.

Does the idle change at all if the AMM is disconnected?
Once you get into adjustable fuel regulators, maybe you'd want a wideband O2 sensor and gauge to see where the AFR is.

I have smoke tested the car quite a few times and do believe every vacuum line has been replaced because it did have a few leaks, i have also swapped the intake manifold gasket and tb, i will however need to check for leaks on the injector seals when i get the chance.

About the AMM, i have been wanting to put that on the suck side aswell because of the reviews on it

Im not near the car at the moment but last time i tried unplugging the AMM(over a month ago) it shut off

another thing is when i was out driving one time turbo blew off the pressure pipes or what you’d call, so the AMM was taking in air directly, and it seemed to be less erratic when idleing

I have fitted an AFR and it sits around 14 but when it stutters or jerks it will either drop to 10 or shoot up to 16-17

Thanks

 

[conehead]

I'd be looking at AMM placement and also spark plugs. I recently had more or less the same symptoms. Checked a bunch stuff before pulling the plugs to find that they were totally toasted, barely any electrode left and the gap was wayyyy off. New plugs in with gap set and now it fires up just fine

 

[FMM]

I'd be looking at AMM placement and also spark plugs. I recently had more or less the same symptoms. Checked a bunch stuff before pulling the plugs to find that they were totally toasted, barely any electrode left and the gap was wayyyy off. New plugs in with gap set and now it fires up just fine

pulled them out a month ago or so and they did look like they were in poor shape so put in some new ones and gapped them to 0.5 but didnt change much, ill be moving the amm soon since ive been hearing that alot

Thanks

 

[DET17]

LH 2.4 vehicle? What does the diagositic port and LED's tell you? Heed those clues is you have that system.

With SO MANY changes, you have a tough road ahead.... could have 2 or more issues, and you might have created them with your changes.

 

[conehead]

pulled them out a month ago or so and they did look like they were in poor shape so put in some new ones and gapped them to 0.5 but didnt change much, ill be moving the amm soon since ive been hearing that alot

Thanks

.5 what?

 

[FMM]

.5 what?

Millimeters

 

[FMM]

LH 2.4 vehicle? What does the diagositic port and LED's tell you? Heed those clues is you have that system.

With SO MANY changes, you have a tough road ahead.... could have 2 or more issues, and you might have created them with your changes.

I have 2.4 but its giving no codes

 

[FMM]

So i had the AMM relocated and it greatly improved the car in general both idle and driving but one issue remains if im driving with 1500-1600 rpm or above and press down on the clutch the car will stall 90% of the time, however if i let it engine brake below 1500 rpm and then press down on the clutch then its fine, dont know what that could be.

Idle is still stumbling a little bit but in general it has gotten better.

 

[OVERDRIVE]

So i had the AMM relocated and it greatly improved the car in general both idle and driving but one issue remains if im driving with 1500-1600 rpm or above and press down on the clutch the car will stall 90% of the time, however if i let it engine brake below 1500 rpm and then press down on the clutch then its fine, dont know what that could be.

Idle is still stumbling a little bit but in general it has gotten better.

I've had tps's that wouldn't read right when you'd lift off throttle quickly, but if you were gentle on it it would register that there was no throttle. I'd adjust the tps and clean the idle control valve.

 

[FMM]

I've had tps's that wouldn't read right when you'd lift off throttle quickly, but if you were gentle on it it would register that there was no throttle. I'd adjust the tps and clean the idle control valve.

Thanks ill give it a go, any good tips for doing so?

 

[OVERDRIVE]

Thanks ill give it a go, any good tips for doing so?

Adjusting? Alligator clips on the tps connectors to a multimeter, then use a feeler gauge between the stop and the linkage. There's a spec for it, I can't remember right now. Listening for the click is unreliable.

 

[FMM]

Update

After putting on a new tps and adjusting it properly i think the issue is fixed, ive only done a short test drive but no stalling

Thanks to those who contributed

 

[FMM]

Hi hoping to revive this thread because i have an issue i cant seem to find answers to, car is running fine now most of the time, one issue remains tho.

When cruising there is no issue no matter at what speed, but if im going 80 km/h and slow down to lets say 50 km/h the car will run lean and jerk for a little bit until it “catches up” then its fine, the issue can be solved by just going full throttle but in traffic its not ideal

Thanks in advance