JWade7

The other day I was driving my 1991 N/A 300ZX. I was going about 40 mph and hit a very large pothole very hard (my right front tire was the one which went through it). After I hit it, my car immediatley made a loud sound, i think it was a loud screeching sound. I pulled off the road and looked to see if there was any visible damge to the car and i found nothing. I popped the hood and likewise saw nothing. I tried to start the car again but it would not start. When I try to start it, it sounds like it is going to start, but it doesnt 'catch' and will stall. I cannot figure out what is wrong with it. A local tuffy has been looking at it for a few days and has ruled out obvious things (i.e. a belt coming loose). Does anyone have any ideas as to what could have happened?

CanyonCarver

considering the impact, I'd start checking electrical connections, then fuses, and maybe relays.............. for starters.

Even more so, some cars have a fuel pump cutoff switch that is impact sensitive. Ie: designed to cut power to the fuel pump in case of impact or rollover. It's basically a red reset switch somewhere. I had some kid throw his roller blades into the trunk of my car one time and it threw the switch. It took me a while (10 minutes or so) to figure that out..............

JWade7

I just called the Tuffy which has my car and they said that it seems like the car is only getting power to 3 cyclinders. They are able to start the car, but it barely runs. There is no problem with the fuel, air, or spark, each is working fine. They said that the plugs on the left 3 cylinders are practically turning black while the ones on the right three still look brand new. Again, they can start the car, but if you put it into gear it doesnt have enough power to go anywhere and it immediatley stalls. Any ideas?

SHWAZ300

Hmm maybe your timing got thrown off somehow, i dont think thats to possible but the reason it could be running really bad is the timing.

JWade7

It turns out my timing belt was the culprit-the timing in my car was actually off 20%. I am, however, very fortunate that my valves were not damaged

bardabe

very fortunate

91zxtt

and bizarre.

JWade7

The place that has my car is now telling me that there is no compression in my car and the valves are bent. Could anything else other than bent valves cause a loss in compression? Would the timing belt had to have completely break and come off for my valves to bend? Does anyone have any idea what could have caused my timing belt to jump 20% after hitting a pothole? I know the timing system is a closed system so it could not have been debris from the road. Could something in the car have jarred loose which caused my timing belt to jump? Does anyone have any advice or ideas? Has anyone ever seen anything liek this before? If I do have my heads and valves replaced, about how many hours would it take a skilled mechanic to do the job? Please help!

91zxtt

Hmmm. A compression test is an easy test for any shop. If I were you, I'd have them complete the test with you there so that you could see the results 1st hand.

This is a stretch....It is possible, yet highly unlikely that you could've jarred your tensioner loose when you hit the pot hole if the tensioner wasn't tightened properly when it was installed. If this happened, then it could've caused your belt to slip. If it slipped far enough, yes it could've bent valves. Another cause of lost compression is a broken piston or broken or seized piston rings. If the piston hit the valve hard enough, then it could've punched a hole in the piston. Since you were only doing 40, you probably weren't spinning the engine fast enough to break a piston. It's not your rings. Rings break or seize usually due to insufficient lubrication, or under race conditions when you're placing excss strain on the motor. Even still, it's very unlikely; especially in the VG30.

Replacing the head is a very labor instensive job. You're basically loooking at a timing belt job (4 hour job) plus a knock sensor replacement (4 hours again), then removal of the heads and the rebuild. I'd estimate 10-12 hours, maybe even 14.

I've never heard of this happening.

JWade7

It looks like, if indeed my valves are bent, I might have to end up putting a new engine in the car. This really sucks because I bought the car two weeks ago, drove it for three days, and it has been in the shop since then. I did, however, find out that a guy who lives in my neighborhood owns the same car I do and also owns a shop, so I may have finally found a mechanic that I trust. Plus, if i do get a new engine i will get to see him install it and I might learn something. I am taking the car from the hop that has it today and taking to this guy to see if it was my timing belt which even caused the problem in the first place, it may turn out to be an overlooked electrical problem. How difficult is it to put a TT engine in a naturally aspirated Z?

b300z

just ask schwaz...he will tell ya