156 SW 2003 1.8 TS stalling on acceleration - Alfa Romeo Forum
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(Post Link) post #1 of 6 Old 20-09-16 Thread Starter
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156 SW 2003 1.8 TS stalling on acceleration

I'm trying to sort out why I keep losing power on my 1.8TS. It started while I was cruising on freeway. A suddent jerk with engine management failure blink and 1-2 sec later all felt fine. While on the same freeway it got bad as the jerking was constant and I had to struggle to keep speed over 80km/h and not get stranded on the freeway.

The car idles fine for long time. The problem usually manifests it self when I try to accelerate. I think it will always happen when accelerating from 40 to 80km/h on 3rd gear.

First I thought it was the spark plugs so I changed the whole set and cleaned the plug holes, caps and wires. Then I cleaned the grounding bolt beneath car battery. I did the reset procedure with unplugged battery and 90sec MAR, 90sec OFF etc...still stalling. I took a graph from OBD on MAF reading and all seemed fine until the MAF readings stopped and car stalled...after 5-10 sec MAF readings came back and car works fine. Ok, it's the MAF that is broken...or so I thought. I bought a new Bosch MAF but still the same problem!

I'm running out of ideas what to do next. My only straw is that perhaps the MAF was installed so that the loose airfilter box lets the MAF connector rub against the bonnet and the wiring harness is broken. I'll need to test that theory but I'm open to any other suggestons. I did check that battery voltage is ok since that was a pinned "fix" on some of these engine management errors. Also I'll try to log more data with multiple datasets to possibly pinpoint the problem.
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Originally Posted by mseger View Post
I'm trying to sort out why I keep losing power on my 1.8TS. It started while I was cruising on freeway. A suddent jerk with engine management failure blink and 1-2 sec later all felt fine. While on the same freeway it got bad as the jerking was constant and I had to struggle to keep speed over 80km/h and not get stranded on the freeway.

The car idles fine for long time. The problem usually manifests it self when I try to accelerate. I think it will always happen when accelerating from 40 to 80km/h on 3rd gear.

First I thought it was the spark plugs so I changed the whole set and cleaned the plug holes, caps and wires. Then I cleaned the grounding bolt beneath car battery. I did the reset procedure with unplugged battery and 90sec MAR, 90sec OFF etc...still stalling. I took a graph from OBD on MAF reading and all seemed fine until the MAF readings stopped and car stalled...after 5-10 sec MAF readings came back and car works fine. Ok, it's the MAF that is broken...or so I thought. I bought a new Bosch MAF but still the same problem!

I'm running out of ideas what to do next. My only straw is that perhaps the MAF was installed so that the loose airfilter box lets the MAF connector rub against the bonnet and the wiring harness is broken. I'll need to test that theory but I'm open to any other suggestons. I did check that battery voltage is ok since that was a pinned "fix" on some of these engine management errors. Also I'll try to log more data with multiple datasets to possibly pinpoint the problem.
Try measuring the fuel pressure, could the regulator... Other thing which I highly doubt is the crank position sensor. If it's packing up the ECU can't determine when to ignite and engine stalls.. Have you any problems with cold start?
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Try measuring the fuel pressure, could the regulator... Other thing which I highly doubt is the crank position sensor. If it's packing up the ECU can't determine when to ignite and engine stalls.. Have you any problems with cold start?
Cold start works very well. That was one thing that got me suspecting crank sensor. I'll test it cold. I'll see if it will accelerate normally. I have a feeling I haven't experienced the problem at all when the engine is cold.

How do I measure fuel pressure?
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Looking at the fuel rail. On one end is the fuel regulator on the other are both in and out pipes remove the pipe which indicates fuel going back to the tank and put a manometer/gauge and see what the pressure is, should be 3BAR +-. Check for cracks on the ignition coils.
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Warming up a crank sensor gets them to throw a wobbly.

What are the plugs like? You could be over or under-fueling. Over-fueling could be the MAF thinking you are still in cold mode and adds fuel like an odd-fashioned choke.

Also what temp is it running at?


Have you tried looking at the diag codes?
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PROBLEM SOLVED!

It was a faulty crank position sensor. That was an interesting part replacement to do on the driveway. Only tool needed was 5mm allen key.
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