94 850 turbo with intermittant starting/missing.

calbrit01 · Post by **calbrit01** » 08 Jan 2008, 16:54

Originally motor was running rough at startup until out of the driveway then seemed to be fine. Replaced a vacuum hose and cleaned the MAF, and that issue has largely gone away.
Now the motor seems to take a long time to turn over when cold, not excessive maybe 3-4 seconds. I have used many fuel cleaners including Sea-foam, and replaced the fuel (and air) filter, checked all the vacuum hoses, and new plugs - After the "cleaning" the next cold start fires straight away ( i.e 1 second ), but then returns to the "long start". also, I am getting a surging/reduction in power sometimes, feels like missing but tends to go away - seems to happen mostly in the first 1/2 mile or so of driving from cold, but idles fine. Any ideas as to likely cause?

SAL

sam1 · Post by **sam1** » 10 Jan 2008, 05:13

Hi,

Read my update above. I think you have a fuel pump issue as well. But first, start with the fuel filter, and new plugs/rotor/dist cap. My old fuel pump had all this crap stuck to the bottom of it, on the screen. The gas tanks on these cars really do accumulate a lot of crap at the bottom. Maybe just taking out the fuel pump, checking to see if all the hoses are on tight, and cleaning the screen.

bobsnow100 · Post by **bobsnow100** » 10 Jan 2008, 07:43

I would check the distributor cap,rotor,spark plugs and replace if they look old or burnt. Important to check the spark plug gaps also. The gap gets bigger all the time and will cause delayed starting.
Has the pcv system been cleaned and or replaced. That can cause the surging if it is clogged, vacuum leaks can cause these problems also

calbrit01 · Post by **calbrit01** » 14 Jan 2008, 14:28

Great, thanks some good suggestions there - never new there was an additional filter in the fuel pump and the spark plugs would regularly need re-gapping.

farupp · Post by **farupp** » 15 Jan 2008, 10:56

If you are using the recommended Volvo platinum spark plugs they should not be regapped. If you are not using them, you should use them.

When I first bought our Volvo, I put a set of Bosch platinum plugs in my '96 850 turbo and it ran horribly. I then read some posts on this forum and immediately bought the recommended Volvo turbo plugs from the dealer. They made a huge, positive difference, and they are pre-gapped.

Post by **MadeInJapan** » 15 Jan 2008, 15:05

Pre-gapped or not, I always check them. Why? Because Volvo sells the same (part number) turbo plugs for both of our cars ('98 S70 and '04 V70) and the gaps are different for these cars. I figure that with newer models being more prevalent, it's a matter of time before the gap on these plugs get changed to what the newer cars run (.030 vs. .028)...sure it's not a big difference but with my ECU upgrade I gap my plugs down to .025~.026.

calbrit01 · Post by **calbrit01** » 22 Jan 2008, 12:16

Ok Interesting thread on the plugs. I removed and checked mine this weekend, mine are Autolite platinum, replaced about 10K miles ago. The old ones looked ok, but were marked "Volvo" so just assumed they were the originals, and at 120k miles were overdue for replacement.
Anyway, the first thing I noticed was the plugs were a light gray color, indicating it may be running lean? - this would make sense with the delayed starting - tried giving it some gas when starting and seems to start better.

As far as gapping is concerned, I hardly find it an exact science. Some of my plugs "appeared" to be as wide as 0.040, some were "around" 0.028. I used a set of expensive feeler gauges and gapping tool, and cross referenced with another cheapo "variable disk" type of gauge, but was still not confident the gap was exact. Are you guys using anything special to set your plug gaps or just general feelers - if you arn't using anything special then I really can't see how then can be set to exactly 0.028, there is just too much margin for error.
After all that, it made no difference to the cold start or the running performance, so I am thinking the running lean is the problem - is there anyway of adjusting that anyone knows, or is this a ECU repair job?

Thanks

SAL

Post by **MadeInJapan** » 22 Jan 2008, 14:25

If you're still having problems, autolite plugs is your problem...just about the worst plugs to use in our cars. And yes, I use a feeler gauge and am meticulous on making sure the gaps are exact...it is an exact science in my book.

calbrit01 · Post by **calbrit01** » 22 Jan 2008, 16:09

Ok I will swap the plugs out, I am guessing the consensus of opinion is the dealer supplied platinum plugs specifically for a turbo? I hate having to go and pay dealer prices.

Maybe my "problem" with setting the gap exactly is because of cheaper materials on the Autolite plugs.

I have also seen some posts that suggest the MAF sensor can cause a lean burn problem, although no code is showing for that, just that stupid knock sensor I can't get rid of which now I come to think of it I also read somewhere this could cause the knock code. What is the recommended way to clean the MAF sensor, I heard someone say there is a specific cleaning product for the MAF?

Thanks

SAL

Post by **MadeInJapan** » 22 Jan 2008, 16:49

SAL, yeah I use the Volvo branded turbo plugs but many people with turbo's use the regular copper Bosch with good success. I would try that first...at least that way you can rule out the plugs. If in doubt which ones, you want the FR7DC.

To clean the MAF, just spray the sensor inside with contact cleaner, or autozone (and others) sell a MAF cleaner. Douse it real good but don't touch it...then let it air dry.