GM I-4 Timing Chain question

[DaveN]

My mother in law's 91 Grand Am (67k miles)is acting up, and I was asked to take a look at it. By the way its acting, I think the timing chain either jumped time or broke. I'm getting spark, fuel, and backfiring through the throttle body, but it won't start. I'm going to give it a compression test tonight, but anyone know anything about this? I believe it's the 2. 5L four cylinder, not the hipo quad 4.



Doesn't this engine have a tensioner that is problematic? Also-is this an interference engine, meaning that if it's out of time do the valves hit the pistons?



What kind of job is it to replace/repair this?



Thanks, Dave

 

[Lnwing]

Grand AM

Dave;



This won't answer your question, but seeing this post hit a raw nerve. We have a 96 Grand Am with the Quad 4. The waterpump gave up recently and cost me $866. 00 at the dealer to replace(including hoses, belts and chain tensioner). Labor is the big item because the pump is driven by the timing chain, and a real PITA to replace.

Our regular mechanic wouldn't touch it. He had done one, and that was enough. "GM built it, let them fix it!"

The GM mechanic said that they always recommend replacing the tensioners if the chain is accessed, so it would sound like it might be a common problem.



Sorry for my rant. Hope your fix is easier.



Lynn

 

[Shelby Griggs]

I too own a grand Am, a 1989 with 223,000 miles. I have the Quad 4 (VIN D) motor. I had the timing chain replaced at around 100K, because I thought it was noisy. In the quad 4 motor at least the timing chain is a double roller chain, a pretty durable setup. The tensioner is hydraulic actuated by engine oil pressure.



I have had the water pump done twice, and it is a PITA. Cool design, but not very user friendly when it comes replacement time. They seem to be good for maybe 100-125K. I paid to have it done, because of the pain that it is, but it seems like I paid "only" around $300, but my memory could bad.



Shelby

 

[Hillbilly Hotrodder]

2.5 repair

I can help on this one. My previous job was working on mail trucks with the 2. 5 liter engine. We had a lot of problems with the cam gear stripping the teeth. This engine uses two gears which mesh together. There is no chain. The cam gear is fiber and gives up the ghost after awhile. GM says that you have to pull the cam and press the new gear on.



Here's the trick. Do it this way and you don't have to pull the cam and press anything, even on front wheel drive applications. First off, tap the camshaft center for a bolt. I don't remember what size tap we used. The cam has a hole of sorts already in it. Just tap some threads into the hole. The finer the threads the better. Now, destroy the cam gear with a chisel and hammer. You will be able to fracture the gear with a sharp chisel.



Now, use the hole that you tapped, along with a bolt and washer, and pull the gear onto the camshaft by tightening the bolt. Make damn sure you have the timing marks right.



Using this method, you don't have to remove the engine and camshaft. Make sure and not allow any pieces of old gear or shavings down into the oil pan.



If I've confused you more than helping, just PM me and I'll try to help all I can.

 

[DaveN]

Thanks for the reply Hillbilly (and others)- according to the Chiltons manual I just got from teh library, they said in 91 the 2. 5 had a regular chain with a tensioner, they stopped doing the double gear thing in 89? at least that's the way I read it. Funny thing is though, according to the pictures my engine looks like a 89 or earlier engine, but according to the text, it has the chain... . I guess I'll find out when I dig into it.



Now when the gears gave out, was there any valvetrain damage, or was there enough clearance? From the sounds of it, it doesn't do any damage, I hate to get into this and find out I need to redo the head as well... .