85euro928

A little history: I’ve always had problems with the car hunting at idle, with bucking at around 2k RPMs, and with a strong fuel smell at the exhaust (typical Euro stuff). In the past to combat this every Spring I would install a temporary wideband O2 sensor and tune the MAF using a VOM. This would get me close but I would then need to tune the CO adjuster by ear to get the car to run well. This usually put the MAF pot ohms around 600.
Recently I removed the two rear FPR’s (euro), and replaced them with an adjustable FPR and a damper, I also added an LC-2 and a new wideband. Using this new set up this Spring I ran the LC-2 software Logworks and set to tuning but was only able to get the AFR to better than 15 by tuning the MAF pot to somewhere near 900 ohms. Figuring the MAF was desperately in need of a rebuild (and not wanting to drive 700 miles to SITM with a bad MAF) I sent it out to be rebuilt.
Yesterday I installed my rebuilt MAF but the results were very disappointing as the car ran worse than it ever has. The engine was hunting so bad that it wouldn’t stay running. After fiddling with the MAF pot without success I called it a night.
This morning I did the following:
• Set fuel pressure to 41.5 psi with the relay jumped, this gave me 32psi at idle.
• Started the car, warmed it up, and set the idle to 750 RPMs.
• Adjusted the MAF pot at idle from 382 ohms (+/- 16 AFR) to 1073 ohms (13.7 to 14.2 AFR).
This gave me a good idle AFR but when I opened the throttle the AFR jumped to more than 16 at about 4000 RPMs! Prior to having the MAF rebuilt when you opened the throttle the AFR would stay the same or go down, now the AFR goes up???
A little troubleshooting gave me the following results:
• With the car running and the MAF disconnected I have essentially 0V at pins 2&4 of the MAF connector.
• With the car off and relay XVI jump between 30&87 I have essentially 0V at pin 7 of the LH connector.
• I do have 4 ohms between pins 3&5 of the MAF connector.
• The vacuum reading at the front fuel damper is approximately 15 in.

I’m thinking that I have two problems, one is that somehow the rebuilt MAF is fragged and second is that I have a vacuum leak which is causing the fueling issue.

I'm going back out to the garage now and will check the fuel pump delivery rate, and even though the car had a top-end refresh done three years ago I think I'll smoke test the intake.

Any thoughts on the MAF and any other checks I should do before I send it back? Anything else I should be looking at in terms of fueling? TIA!

85euro928

I just checked my fuel flow rate. According to the manual it looks like I'm supposed to be getting 1350cc in 30 seconds on the return line. I just measured mine and I'm only getting 1000cc in 30 seconds, would this cause my high AFR? Also, is this a sign of a dying fuel pump or something else?

Pfc. Parts

It seems very unlikely your recently rebuilt MAF is no good. Much much more likely you have a pretty severe vacuum leak. You don't mention who re-built your MAF, but I understand John Speake and his US associate bench test them before returning them to you.

I'm siting here in the reply window and can't see if you posted your model year. From the intake it looks pre-85. I'm not very familiar with that year, on the '85 I'd suggest removing the intake manifold and checking all the rubber vacuum lines for holes and cracks.

Pfc. Parts

Sorry Thom, I see now you've posted it as an '85 Euro (which looks like an '84 to me due to the manifold design). Same advice then. I'd pull the manifold and look for leaks. It worked for me.

John Speake

Intake vacuum should be around 21"Hg. Fix that and then see how things measure. It's VERY unlikely your new rebuilt MAF is the problem. Sounds like the car has some underlying problems.

85euro928

Working on smoke testing the intake now and will report back. However the intake was redone (by me) 3 years ago so unless there's a disconnected hose I haven't been able to visually find something else is majorly screwed.

Pfc. Parts

Here's just a guess. You replaced the MAF recently? Did you make sure the O ring at the bottom of the MAF (between the MAF & throttle body) didn't fall off into the V while you where installing it? That happened to me several times before I figured it out.

85euro928

Scott,
Both O-rings are in place, good guess though.

85euro928

John,
What would cause me to have 0 volts at the MAF and LH plugs? Bad ECU? As you may remember the ECU's are new-to-me, maybe one failed?

928wolf

I have similar problems on my 85Euro as well and plan on doing the fuel flow test tomorrow. If I measure a low fuel flow rate by 25+% I will be pretty concerned, and would probably replace the fuel filter (first) and fuel pump (2nd). It seems to me that this wouldn't be a big deal for idling but would start showing up at high rpm and load, which is my problem. Mine is sputtering in falling into a hole in the prime torque band 3000-5000+ rpm. My power is very inconsistent, "bucking" under light load and jerking and sputtering under high load.

Very interested to see what your problem turns out to be.

Randy V

It doesn't appear you have a forced induction system installed so I'm wondering why you have made all these modifications to the stock system?

85euro928

Randy,
Why the AFPR? In speaking with DR a while back he was saying that the Euro's have a tendancy to run lean and require additional fueling. When my rear damper went it was an easy decision to make the change. The change definitely helped with the bucking and lean issues.

85euro928

Wolf,
The fuel filter is probably 4 years old so I'm thinking it's the pump. Question is will this rate of flow cause the leaning issue?

928wolf

I'm certainly not knowledgeable enough to answer that question.

But, some simple math (if I did it correctly) says that if 1350cc(1cc=1ml) per 30 seconds equates to 162 liters per hour, so at full rate the fuel pump would empty the 86 liter fuel tank in about half an hour. Even the most spirited driving wouldn't run through a tank full in that short of a time. So that tells me that at any condition short of full throttle and load the engine does not need nearly that amount of fuel. So, I would think even 25% less fuel flow would only affect the engine near full power. If all of that is true (I make no guarantees that it is) then the fuel flow rate probably shouldn't make you run lean except maybe at the max power condition.

That's just off the top of my head thinking, I'm sure it's not quite that simple with these complex machines, I'm sure somebody will be able to tell me where I'm wrong and give a better answer. I'd really like to know the answer myself.

928wolf

My simple thinking is a fuel filer costs $20, a fuel pump $250, so I'd like to rule out the cheap solution first