Hi all,

I have a 96 850 turbo 103k. I am trying to diagnose a misfire all cylinders. I have replaced all of the common tune up parts.

plugs (volvo - proper gap)
Wires (bogicord)
Cap and Rotor (bosch)
ignition coil Karlyn

New air filter

The only codes that I am getting is for misfire cylinder 1 through 5 and random misfire.

The car idles good. It does not sound like I have a vac leak anywhere.

BTW, The misfire is intermittent. SO, I don't believe it to be a timing issue. And since it is all cylinders I am thinking that it is unlikely to be a compression issue. (all assumptions).

Can anyone point me in a direction????

It's most likely gas. Always run premium and you will be fine. Our 1993 GLT, NA, has run on premium from new and never had a problem. You will get high MPG too. Try Chevron with techron, re-set codes and see if that does it.

Well, I took off the guard that covers the injectors and I sprayed brake cleaner around the intake manifold. I did not get a change in idle. I noticed that the top right bolt of the intake was missing. So, I concentrated spray in that area. I still did not get the idle to change.

I have visually inspected the vac lines and I can't find any holes.

I am wondering if my o2s are causing a rich mixture which is in turn fouling the plugs and giving me a misfire all cylinders.

I still need to check the pressure though. but I got to thinking. If it is a low pressure isn't that only going to show up when it is misfiring.

I need to pay more attention to when the mis is happening.

I got that code and my coil wire from coil to dist cap was fried at the cap. broke right off..

I recently got multiple missfire codes when my MAF went bad but it was definitely not running well at the same time. Would not idle. Maybe try reseating the MAF plug. Also check the air filter thermostat. They often fail and allow heated air to be sucked in all the time. This could affect the MAF operation. Check the intake bellows also they tend to crack over time.

In most cases, you will not hear a vacuum leak. The engine will run rich if there is one, and adding more gas at low rpm will cause the plugs to foul. Visually inspect all of the many lines, especially the hidden vacuum line behind the power steering pump.

Klaus
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Always willing to listen, just not able to take direction.

Yes, I have done the elbow by the power steering pump. That line had a hole in it and I was getting a code for fuel system to rich or lean -- can't remember. Fixed that elbow and code went away.

I will keep checking for Vac leaks. Klaus, I have seen that you can spray a brake cleaner around vac lines and gaskets like the intake and if the idle changes then you have found your problem. Is this a good idea?

Also, I went out and bought a cheap fuel pressure tester today that will hook up to the schrader valve. Any chance that my fuel pressure would cause the issue?

If it turns out to be a vac leak that is screwing with the fuel mixture and thus fouling plugs I think I will go with a different plug next time. Those volvo plugs are spendy and I was reading that there is another plug that will work with this car. Can't think of the brand off top of my head but it seems like it is a cooper plug not platinum.

If the vacuum leak is large, then the brake cleaner will change the idle. Very helpful when checking the intake manifold gasket.

If it is fuel pressure, check the vacuum lines to the fuel pressure regulator. I think 1996-8 the FPR is behind the block, down on the subframe. Just follow the fuel line. On 1995 it is next to the #1 injector.

When checking the fuel pressure, it should be around 42lbs at idle.

I like Volvo branded plugs, they last 50K miles or more. If they are gummed up, just clean them with a wire brush and set the gap at .028 Other brand copper plugs last around 15-20K miles.

Klaus
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Always willing to listen, just not able to take direction.

Thank you very much. I will try these different things.

Tell me if I'm wrong but..... How does the ECM know if there's a misfire if it correctly sends a signal for the sparkplug to fire in the right sequence but it doesn't result in any explosion or a weak explosion due to a bad mixture? Just don't understand how the ECU could know if the mixture exploded or not. As long as it's putting out the right spark signal at the right time you shouldn't be getting any misfire codes. Have you tried any higher octane or different brand of gas?? How's the air filter??

The engine doesn't detect misfires from whether the spark goes, but from "watching for misses" on the flywheel. Here's much more info on it than you asked for:


Misfire diagnostic

If the fuel/air mixture does not combust in any one cycle or does not burn as it should, the engine is said to be misfiring. The engine control module (ECM) can detect misfiring. This is done by recording the time between two segments on the flywheel/carrier plate.
This time can vary due to the following reasons:
*misfiring
*flywheel mechanical tolerances
*driveline oscillations
*normal variations caused by uneven combustion
*poor roads.
Since mechanical tolerances and drive train oscillation interfere with the signal, it is difficult to ascertain whether or not this interference is due to misfiring. To eliminate mechanical faults in the flywheel the flywheel signal is adapted. Two crankshaft revolutions are divided into five periods, if the engine is unloaded all five periods should be equal.
This is to even out the signal, so that a mechanical fault in the flywheel is not registered as misfiring.
After adaption there is still some interference in the signal. This is because of oscillations in the drive train and normal engine irregularities.

The flywheel signal is adapted when:
*engine speed is between 1200 rpm and 3000 rpm
*the fuel shut-off system is operating during engine braking and has been active for 30 ignitions.

Flywheel signal adaption finishes after 40 second's accumulated fuel shut-off within that engine speed range.
The accelerometer signal is used by the engine control module (ECM) to determine how much the car is moving vertically and longitudinally, on a bumpy road for example. These irregularities can cause the engine to run unevenly. The engine control module (ECM) uses this signal to differentiate irregularities from real misfiring. Misfire diagnostic is disabled on bumpy roads.

Misfiring lights the malfunction indicator lamp (MIL). If there is a risk of catalytic converter damage the malfunction indicator lamp (MIL) flashes for as long as the misfiring continues, it then lights continuously.
The engine control module (ECM) registers and stores the engine speed and load range in which the misfiring occurred. The malfunction indicator lamp (MIL) lights if misfiring occurs again within the same engine speed and load range. If misfiring ceases, the engine must go through this entire engine speed and load range without a misfire before the engine control module (ECM) starts counting down to put out the malfunction indicator lamp and erase the misfire codes.
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If you're not driving it "like its stolen," are you really driving?

Thanks...didn't think the ECU was that smart!!!

We usually run the cheapest gas. I hear a lot of people talk about the highest grade fuel for the turbo only. I think I should try to run the higher octane for a month and see if misfire goes away.

When you buy cheap gasoline, here is what you get:

No added cleaners to keep the combustion chamber clean

Poor performance at higher rpms

Pre-detonation, pinging which you won't hear.

The cheap gas (low octane) will cause predetonation (the cheap fuel burns faster), and that causes the knock sensors to alter the timing and/or add fuel to eliminate the knock. Even worse on hot humid days. This will lower your fuel consumption and leave deposits on your cylinders and valves. It will also help coat the O2 sensors with soot, and wear out your catalytic converter.

Do two things: Change or clean your spark plugs and fill up with premium to get the octane up to at least 89. Contemplate using Seafoam head cleaner.

Klaus
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Always willing to listen, just not able to take direction.

I would like to try and clean the plugs since they are expensive volvo plugs and relatively new.

I have never cleaned plugs and am worried I may damage the electrode. I remember you saying to use a wire brush. Should I look for a certian type of wire. It seems like there is a steel, brass, etc. And do I use any spray cleaners? I will make sure to check for gap after.

I will google search this but thought I would check here since this thread is going.

BTW, I went with a mid grade fuel last time around and I have not noticed a misfire since. Today I plan to get a fill with a premium.

I like brass bristles best, you can use them on more metals than steel.

Just brush off the carbon from the plug tips and the threads. The brush will not harm the ceramic. No spray is needed, the plugs do not have to look new, just relatively clean.

Sounds like your cheap gas caused the timing to be retarded and you will find the plugs nice and black, covered in soot.

When you think about the difference in price, remember that each grade of gasoline is only 10 cents/gallon more than regular. That is $1.80 more for a full tank, and that should be no big deal.

Klaus
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Always willing to listen, just not able to take direction.

Good Afternoon,

Try this out.
(below)

P.i. Performance Improver Concentrate (API)
Improves fuel mileage an average of 2.3% and up to 5.7%. Reduces emissions such as hydrocarbons (HC) up to 15%, carbon monoxide (CO) up to 26% and nitrous oxides (NOx) up to 17%. Restores power and performance. Reduces the need for costly higher octane fuel. Reduces noise from carbon rap and pre-ignition. Offers better vehicle drivability and smoother operation.

Untreated Fuel Leads to Poor Engine Performance
A vehicle demonstrates its best efficiency and engine performance when it is new. As the engine ages, its performance suffers from gasoline fuel-generated deposits that form on the fuel injectors, intake valves and combustion chamber. Additives are required to control deposit formation.

Today’s fuels, however, lack sufficient treatments of either enough additives or high quality additives. Fuel system deposits result in the following:

• Lost fuel economy
• Lost power and poor throttle response
• Failed emission tests
• Poor drivability - surging, hesitation, stalling, rough idle
• Engine knocking (pinging) and rap
• Difficult starts

Treated Fuel Delivers Maximum Performance
AMSOIL P.i. is the most potent gasoline additive available today. As a concentrated detergent, it is unsurpassed in cleaning combustion chamber deposits, intake valve deposits and port fuel injector deposits. AMSOIL P.i. helps maintain peak engine efficiency, fuel economy, power and drivability in newer low mileage engines. In engines with accumulated deposits, testing showed AMSOIL P.i. provided the following clean-up benefits after only one tank of gasoline:

• Improves fuel mileage an average of 2.3% and up to 5.7%
• Reduced emissions
— hydrocarbons (HC) up to 15%
— carbon monoxide (CO) up to 26%
— nitrous oxides (NOx) up to 17%
• Restored power and performance
• Reduced need for costly higher octane fuel
• Reduced noise from carbon rap and pre-ignition
• Better drivability
• Smoother operation

AMSOIL P.i. works as an “emissions passer.” It is ideal for use prior to emissions inspections.

This should help make a difference!

I use only the best synthetic oils, oil & air filtration products in the world. There is absolutely no comparison Amsoil is the Best at what they do!

So for any of you who want, need or learn more about Amsoil, contact me at rpiescik@weareoil.com

Glad that you're so enthusiastic about the products you sell, but if every auto parts dealer started posting like this, Brickboard would soon be overwhelmed with garbage. There's enough of that already. Especially irksome if you're not even a financial contributor to help sustain the board.

Just my $0.02 ...

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'96 850T and '83 244 DL both at about 200K, '97 850T5; gone but not forgotten '81 245 and '64 Amazon

how exactly does it reduce emissions?

In the PI tests, there is no control listed. How did you account for normal deposit burn off due to running it on the Dyno?

What gasoline was used? Was it gas conforming to Top Tier standards, 87, 89, 91, 93, etc?

How does this compare to an Italian tune-up?

Are you supposed to add the bottle to every fill up? The $2 saved in not using premium gas is going to be destroyed by spending $10 on a bottle.
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If you're not driving it "like its stolen," are you really driving?

Horse pilss!

Have you checked fuel pressure.. Is it misfiring under load, no load, both, or you have no idea?
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If you're not driving it "like its stolen," are you really driving?

I think it is misfire under load because I feel it on the highway, and in the morning when I am driving up this steep hill by my house.

Oh, and I have not checked fuel pressure. I was thinking that would be a good next step. The fuel filter is maybe a year old. I will have to check but I may have wrote the date mileage on it when I replaced.

I was thinking that maybe I have a pump putting out low pressure and that is the reason for the misfire on all cylinders.

Just guessing here.

It might be the fuel pump relay then. The thing is two stage, one for idle/low rpm, the other for high use. If the second stage is gone, it wouldn't be getting enough Amps to give you enough juice. If its consistent enough, you could try jumping the FPR and see if it the misfires go away (IE steep hill). However, the pump stays on when the keys in position I or II, so be aware of possible safety issues.. The relay is in under the plastic guard by the fuses. Its 4 torx (T-25?) holding the cover down, and I believe the relay is marked 102. Jump pins 15 and 87 I think (top and bottom center I know that..) and take it for a spin. Misfires go away, you found your problem. You can use one obtained from a Pick-n-Pull for about $5, less if you like to haggle.
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If you're not driving it "like its stolen," are you really driving?