1997 850R rough idle after head rebuild

renzo86 · Post by **renzo86** » 26 Jan 2014, 00:36

Hello Volvo brothers. I've been working on my 97 850R for a while now. I replaced valves and stem seals and head gasket. Now everything is back in the car. As I was installing the timing belt, I thought I got the timing marks right. When I started the car, I felt a very bad rough idle. The car dies quickly unless I push on the gas pedal. I checked the timing marks and found the crank mark moved one tooth to the right (clockwise). Is this enough to trigger this kind of behavior? The cam marks are just fine. I thought cap rotor was faulty and went to buy new one and spark cables as well. All the gaskets are new. Valves, stem seals too. I remember doing a good job when i installed the head. I did a good cleaning job. Now I don't understand why one tooth off would make such a messy idle. I'm gonna check compression tomorrow.

Any comments and suggestions are very much appreciated!

Thanks for reading!

Post by **erikv11** » 26 Jan 2014, 05:34

If the timing is truly only one tooth off, no it shouldn't make that much difference. However check the timing very carefully: put the *crank* dead on the mark, then estimate how many teeth off it is based on the cam marks. You're gong to want to fix the timing now, not later, regardless.

Check all of the vacuum lines for proper routing and make sure none are disconnected, they are the most common cause of rough running after major engine work.

Post by **xHeart** » 26 Jan 2014, 06:24

Search the forum, someone wrote to rotate crank 2 full turn (360º x 2), go pass 1/4 (90º) turn more after the 360 x 2, then counter-rotate the crank 1/4 to align at markers.

Now check the corresponding CAM marks.

Post by **rspi** » 26 Jan 2014, 08:58

Fix the timing and see how she idles. If still rough, check for codes.

Post by **erikv11** » 26 Jan 2014, 09:12

xHeart wrote:Search the forum, someone wrote to rotate crank 2 full turn (360º x 2), go pass 1/4 (90º) turn more after the 360 x 2, then counter-rotate the crank 1/4 to align at markers.

Now check the corresponding CAM marks.

This is for 99+ cars, OP has a 97. Just fix the timing: line up the three marks.

Post by **jblackburn** » 27 Jan 2014, 09:31

My car idled OK even when the timing was off. Power delivery was a different story...

I think you did something many of us have done: the intake manifold may not be seated properly.

In the lower right corner, at the screw, there's a bracket that often gets jammed in between the intake manifold and gasket. Take it out or hold it in place as you're re-installing the intake.

renzo86 · Post by **renzo86** » 27 Jan 2014, 14:16

Update: I took the timing belt off once again. Checked my marks like 10 times. Started the engine and still the same story. One thing I noticed, when I unplug the air mass flow sensor the engine seems to last 1 or 2 seconds more before it dies. If I give it gas, it sure runs but fuel odors start to come out. So I'm assuming my air mass sensor is bad. I have spark, I have fuel, I think the issue has to do with air coming in. Should I just spray some cleaner? Or buy a used one? Does all of what I'm saying even makes sense? Lol.

Thanks everybody.

Ps. I made sure the intake manifold is tight and properly seated. I know about that bracket. It's just holding the vacuum line for the PCV.

Post by **xHeart** » 27 Jan 2014, 15:24

Justin's take is classic, vacuum leak at gasket.
Robert's post would point to fuel supply at fuel rail.
Idle speed sensor is another issue.
Check wires at distributor.

I had cleaned IAC valve and the throttle plate, and replaced vacuum hoses.

renzo86 · Post by **renzo86** » 27 Jan 2014, 18:23

Fuel seems fine because when I push the gas the car stays on. But it sounds like its choking.

I did a compression test and here are the results: 165,160,165,170,170.

I have good compression in all 5 cylinders.

I spray the MAF sensor with throttle body cleaner and same story.

How do you check the idler? Does it really get clogged? I cleaned the throttle body before installation.

My spark plugs are new. My cap rotor and sensor and wires are new.

I'm kinda running out of ideas...

Post by **erikv11** » 27 Jan 2014, 19:08

What brands on the plugs-cap-rotor-wires?

These cares are very picky about ignition parts, especially plugs and wires.

IAC can get pretty clogged, although I am not sure it is the problem here. A clean one, when you shake it you can easily hear the internal gate swing back and forth. Fill it with carb cleaner and shake it until it moves easily, then dump out the carb cleaner. Repeat a couple times until the cleaner runs clearish.

MAF does not sound bad. Be vary careful what you clean it with though, most would only use "electronic parts cleaner" or CRC even sells "MAF cleaner."

This still sounds like a vacuum leak. I know you checked the bracket at the IM, that's good. What about other lines? Is the one on the IM nipple under the PS pump attached?