I recently made a huge investment to have my engine and transmission replaced with one of those used Japanese engines that's guaranteed to be less than 60K miles. Despite the lost of time it's been sitting in the car shop, the vehicle still does not run well. The engine seems to respond with moderate vibrations upon the slightest push on the gas pedal. I noticed that this is not necessarily the case when the engine isn't warmed up. For example, the car doesn't display the now-normal vibrations when I drive it for the first few minutes.
The garage mechanic could not determine the problem. Subsequently, he brought it to another shop with more modern/advance equipment to diagnose the problem. That shop couldn't determine the culprit either. They both confirmed that the engine is good with no error codes. They also confirmed that the injectors and compression test are good as well. As a last resort, the mechanic brought it to the Infiniti dealership to have it look at however I felt that he might have massage the answer from the dealership in telling them that it might be related to the drive line. And sure enough, the dealership came back and confirmed with the mechanic that it MIGHT be a drive shaft problem. The dealership confirmed the vibration upon acceleration, and that the vibration is also noticeable at higher RPM in neutral. The dealership printout also indicated a "misfire", which the mechanic failed to mention until I brought it to his attention. When I made him aware of it, he simply explained that the dealership needs to fix the drive shaft before the misfire could be determined correctly. Because I know very little about cars, I don't know what the mechanic is telling me is factual. I find his explanation, at best, unsettling and suspicious. One last thing I forgot to mention. The mechanic said he didn't tell the dealership that he swapped engines because he wants the dealership mechanic to look into the full diagnostis without any preconceived notions. Does that make sense?
Lastly, I always suspected that the reason my cabin is overflowing with a strong smell of gasoline is because of bad injectors from my previous engine (at least that’s what one mechanic told me), but the same problem persist despite the new engine. Do you have any idea why this is a lingering problem? I appreciate any feedback.
'91 Q45 Engine Vibration after Engine Swap
Hello and welcome to NICO,
I think it's great that you had the engine and transmission swapped. It shows a great deal of dedication to you car. Let's get started on the diagnosis:
Are you experiencing loss of power also or just vibration? There are many things that could be attributed to this. I guess my first question is: when they swapped the new engine in, did they get new motor mounts? if not, I would definitely get those replaced. They are about 200-250 dollars. Other problems could be a bad MAF connection. Have your mechanic try to wiggle around the MAF connector while the car is running. This should tell you if that is your problem. Other things such as O2 sensors, knock sensors, etc. should have been replaced when you swapped engines. A misfire doesn't have much to do with the differential. I think there may be a leaky/faulty injector or a carbon-filled valve. I'm sure Dennis and others will chime in with better answers but like I said there are many possibilities.
The gas smell is one of the following: leaky fuel injector, leaking fuel pump, fuel lines. Another possibility is the valve covers not being re-sealed when he swapped engines.
Hope all this helps and again welcome to our club. BTW, what mileage on the car?
Nick
I think it's great that you had the engine and transmission swapped. It shows a great deal of dedication to you car. Let's get started on the diagnosis:
Are you experiencing loss of power also or just vibration? There are many things that could be attributed to this. I guess my first question is: when they swapped the new engine in, did they get new motor mounts? if not, I would definitely get those replaced. They are about 200-250 dollars. Other problems could be a bad MAF connection. Have your mechanic try to wiggle around the MAF connector while the car is running. This should tell you if that is your problem. Other things such as O2 sensors, knock sensors, etc. should have been replaced when you swapped engines. A misfire doesn't have much to do with the differential. I think there may be a leaky/faulty injector or a carbon-filled valve. I'm sure Dennis and others will chime in with better answers but like I said there are many possibilities.
The gas smell is one of the following: leaky fuel injector, leaking fuel pump, fuel lines. Another possibility is the valve covers not being re-sealed when he swapped engines.
Hope all this helps and again welcome to our club. BTW, what mileage on the car?
Nick
Thanks QShip & 90Q45blue for your fast respond to my post. Also, thanks for welcoming me to the club 90Q45blue! There's no doubt that I'm a dedicated Q45 owner, however recent headaches relating to the engine swap have made me skeptical about Q45s and questionable about long term loyalty to this specific model among the Nissan/Infiniti brand. I hope this forum can help me straighten out some of my concerns.
Nick - let me address some of your questions below...* Yes, I experience loss of power in addition to the vibration upon initial acceleration. It sometime appears as if the engine struggles to rev up w/ moderate vibration before the car actually goes forward. This is particularly embarrassing especially considering the 4-cylinder car next to me can get off to a good start before my car starts rolling.* My mechanic (Johnny) did not replace the motor mounts because he said the old one is still in good condition.* Johnny failed to mention about the MAF, so I assume he didn't suspect that the MAF might contribute to the problem* Johnny mentioned that he had to replace the knock sensor taken from my older engine and it works just fine (for now)* I had the two front O2 sensors replaced (of course with OEMs) as part of the engine swap job, but the two rear 02 sensors are originals
As far as the misfire and gas smell issues, I'll take your (Nick) suggestions to my mechanic and have it looked at more comprehensively. Thanks for giving me some hope that this performance machine should not be easily given up on.
John'91 Q45 w/ 140K
Nick - let me address some of your questions below...* Yes, I experience loss of power in addition to the vibration upon initial acceleration. It sometime appears as if the engine struggles to rev up w/ moderate vibration before the car actually goes forward. This is particularly embarrassing especially considering the 4-cylinder car next to me can get off to a good start before my car starts rolling.* My mechanic (Johnny) did not replace the motor mounts because he said the old one is still in good condition.* Johnny failed to mention about the MAF, so I assume he didn't suspect that the MAF might contribute to the problem* Johnny mentioned that he had to replace the knock sensor taken from my older engine and it works just fine (for now)* I had the two front O2 sensors replaced (of course with OEMs) as part of the engine swap job, but the two rear 02 sensors are originals
As far as the misfire and gas smell issues, I'll take your (Nick) suggestions to my mechanic and have it looked at more comprehensively. Thanks for giving me some hope that this performance machine should not be easily given up on.
John'91 Q45 w/ 140K
If your engine has under 60k on it, and has good power balance and compression test results then it is not the engine itself that is the problem. I'm thinking it's a bad MAF connection. These things are not meant to be unplugged and re-plugged over and over so, unfortunately, sometimes when you have to unplug the MAF then the connector goes bad. Did you have all the injectors cleaned and tested before the swap? If not, get that done now. Your mechanic should be able to clean them and test them for around 50 bucks. The knock sensors should be replaced for sure, along with the knock sensor wiring harness. They should not be moved over from your old engine.
Hope this helps.
Nick
Hope this helps.
Nick
My two cents for what it's worth...Just had my engine replaced a few months ago and ran into a similar problem. I kept thinking that it was a bad fuel pump. It had poor power, hesitation, engine vibration and kept stalling. I replaced the pump and that didn't fix the problem. Anyway, I finallly tracked the problem down to the mass air meter plug (next to the air box). It was very corroded and all bent up. I think when they replaced the engine, they just pulled it out of way and mangled the plug and terminals. I straightened and cleaned the terminals but that didn't quite do it. So then I scraped the black sealant from the top little square door, opened it and found that the three small solders had broken lose. I resoldered them and solved the problem. Very peppy and idles smooth as butter.
robert
robert