Injector resistance check

[olopezm]

Hey people!

I've been chasing this shudder (vibration) between 1000-1100 RPM's for a long time; I have already checked CV axles and engine mounts (new mounts), and all are OK. A friend suggested checking the injectors so I measured resistance across each one and got:

12.8 ohms for 1,2,3,6
12.7 ohms for number 4
12.9 ohms for number 5

Shop manual states resistance spec to be 11.4-12.6 ohms when cold.

Would this increase of .1-.3 ohms cause any drivability symptoms, specially that shuddering?

Thanks in advance,

Oscar.

[gmtech1]

Originally Posted by olopezm

Hey people!

I've been chasing this shudder (vibration) between 1000-1100 RPM's for a long time; I have already checked CV axles and engine mounts (new mounts), and all are OK. A friend suggested checking the injectors so I measured resistance across each one and got:

12.8 ohms for 1,2,3,6
12.7 ohms for number 4
12.9 ohms for number 5

Shop manual states resistance spec to be 11.4-12.6 ohms when cold.

Would this increase of .1-.3 ohms cause any drivability symptoms, specially that shuddering?

Thanks in advance,

Oscar.

No... How about some more info on your shudder. What are the exact conditions it occurs?

[olopezm]

Thanks gmtech1!

I've opened a couple of threads regarding it but never had response, this place seems deserted lol.

This shudder occurs only when revving between 1k and 1100 RPM's. It is more noticeable when in gear (shakes the entire car) but idling in P or N it can still be felt, although barely (you wouldn't know it's there unless you've been in the car before the shudder started). Does not seems to change when moving forward or backward while making circles (guess that should rule out bad CV axles).

For peace of mind I had the CV axles checked and one of them had a broken inner boot which was replaced, re-greased and re-installed but problem persists. Mechanic said they are OK and torn boot was caught on time with no damage to the joint. I decided to get under the car and checked for play on them, these are the videos:

Passenger side (seems to have some play)
http://www.youtube.com/watch?v=dW6Nby08000
http://www.youtube.com/watch?v=VprE7FVbPA0

I asked several people about it but they said it seemed normal and that passenger side joints have normally more play than driver's side, even when good.

Driver side (seems normal)
http://www.youtube.com/watch?v=DGDS11VwW2s

Engine shows excessive back and fort movement when changing from P,N to any gear, it can sometimes be seen slightly wobbling at idle. Another mechanic told me that it was a good practice to loosen all nuts after replacing any mount, so they would "relax" and let the engine rest properly on them, and then start torquing the nuts. I did as instructed but nothing changed. This seems to cause some clunking when driving over bumps, the weird thing here is that it only seems to happen when engine is cold and will go away after driving for a while.

Engine and transmission mounts are new, torque strut mount bushings (dogbones) were replaced with those of a 3100 engine from a junkyard, I couldn't find new direct replacements. Don't know if 3100 bushings are softer than 3800's.

I checked the harmonic balancer to see if it had separated. I put some white marks on it and ran the car at different speeds and loads to see if the marks would split but they didn't. After driving for several months with them, they remain on the same state as they were originally. There are no missing rubber pieces on it either.

Transmission shifts fine and RPM's do not surge at all.

Other than a broken cat converter honeycomb, there are no other problems with the car. No DTC's either.

This shudder started after a shop replaced a cracked head; they took the engine apart to make sure the block was OK, so it's been rebuilt. I took the car several times for them to fix it but I eventually got tired of it and decided no one else would touch my cars!

I don't know what else to check.

Oscar.

[Tech II]

Agree with GMTech1.....those R values are close enough.....but you are not out of the woods....an injector(s) could still be bad.....only an injector flow test(expensive equipment) can eliminate a problem with the injectors....but I tend to doubt an injector for a problem that only occurs at 1000 rpms....

Do you have access to a scan tool....check TPS data for a jump as you get near 1000 rpms.....

[olopezm]

Thanks Tech II

I'll leave the injectors alone for now.

I do have cheap live-data capable scanner but I don't think that it's slow rate will allow me to check for spikes in the reading; I'm guessing a DMM could be used instead of the scanner? Would disconnecting the sensor and driving like that be of any help?

Oscar.

[sim1manson]

Does the "shudder" happen only in drive, or in park as well?

[olopezm]

Originally Posted by sim1manson

Does the "shudder" happen only in drive, or in park as well?

It is more pronounced when in gear, but it also seems to happen (almost unnoticeable) when in P or N.

Oscar.

[olopezm]

Ok guys, so today I checked resistance on the TPS and it does not jumps at all; I decided to give it a try, disconnected it and test drove the car but the shudder persists.

I will CHANGE MY STATEMENT it ONLY HAPPENS when IN GEAR. It does not happens when in N or P, at all. I guess that should point back to a bad CV joint?

Thanks in advance,

Oscar.

[gmtech1]

Originally Posted by olopezm

Ok guys, so today I checked resistance on the TPS and it does not jumps at all; I decided to give it a try, disconnected it and test drove the car but the shudder persists.

I will CHANGE MY STATEMENT it ONLY HAPPENS when IN GEAR. It does not happens when in N or P, at all. I guess that should point back to a bad CV joint?

Thanks in advance,

Oscar.

Only in gear under load/acceleration? If so it may be the inner joints on the axles. Are they the original axles? Reman axles are fairly cheap, 40-60 bucks for a GP.

[olopezm]

Originally Posted by gmtech1

Only in gear under load/acceleration? If so it may be the inner joints on the axles. Are they the original axles? Reman axles are fairly cheap, 40-60 bucks for a GP.

Thank you! I thought so, even when it only happens within that range of RPM's. The mechanic keeps telling me they're OK, I don't fully trust him...

Yes, they are originals. Do you know of a way to diagnose them without taking it apart? I posted two videos in one of my previous posts (for each side) and one of them seems to have more up and down play.

I don't think it's possible with the open differential but would jacking one front wheel at a time and putting it in gear be of any help? (I know it's dangerous and have to be real careful). Another question, how good is the quality of cv axles from autozone? I know cardone has mostly bad reviews for MAF sensors but have no idea about axles.

Oscar.

[gmtech1]

Originally Posted by olopezm

Thank you! I thought so, even when it only happens within that range of RPM's. The mechanic keeps telling me they're OK, I don't fully trust him...

Yes, they are originals. Do you know of a way to diagnose them without taking it apart? I posted two videos in one of my previous posts (for each side) and one of them seems to have more up and down play.

I don't think it's possible with the open differential but would jacking one front wheel at a time and putting it in gear be of any help? (I know it's dangerous and have to be real careful). Another question, how good is the quality of cv axles from autozone? I know cardone has mostly bad reviews for MAF sensors but have no idea about axles.

Oscar.

Can't really tell without disassembly. The only aftermarket axles I have used have been from NAPA. They seem to work out ok..

How many miles are on your car?

[olopezm]

Originally Posted by gmtech1

Can't really tell without disassembly. The only aftermarket axles I have used have been from NAPA. They seem to work out ok..

How many miles are on your car?

Thanks, there are no NAPA stores here, only autozone and a bunch of local chains but I must say that I don't really trust any and these only sell inner and outer CV joints as separate and not as a whole CV axle assembly.

Car has 118k miles on it. The shudder only happens when accelerating from a stop and only within the 1000-1200 RPM range. It will stop above that and there are no vibrations or noises at highway speeds, it will happen until the next stop. It also seems to vary with the load, for example if I start accelerating while going downhill it won't feel as bad as accelerating when driving uphill.

I had my mechanic take another look at them and says they are OK; now I don't now if I should keep trusting him.

Oscar.

[olopezm]

Been trying to diagnose it with no luck. I've only noticed that the vibration will lessen as engine temp reaches normal operating temp. Don't know what could this mean, maybe I got a bad engine mount when I replaced them?

Oscar.

[rkvons]

Have you thought about a tire with a soft spot in it? If parked, it conforms to the ground a certain way and then goes away when the tire warms up from use.

[olopezm]

Thanks, I don't think the tires are the problem as the vibration will be felt even when power braking. It looks like I might have got a bad engine mount and wil have to replace it; durin the last days, from time to time I can hear a slight metal-on-metal squeak when putting the car in R.

Oscar.