OK so i have a 850t fwd auto and I just got done doing a complete engine rebuild, upper and lower. if it has bearings, seals, gaskets, stretch bolts, rings, its been replaced. I have everything back together now, and it will start but when it does, it runs very rough at every rpm(only rev, not under load)and it also backfires like crazy when I give it some gas. I have some ideas what it might be but I want to see if anyone else has advice since im the only brian working on this. the only code it threw after the build was 2-1-4 which is rpm sensor but I took care of that. I double and triple checked my timing and i cant get it anymore perfect. I know im not 180 out.

Here are a few things about the car to give you some ideas:
IPD ECU upgrade- newish
volvo spark plugs, wire, rotor, cap-new
fuel pump relay-new
18t turbo-new
IPD cold air ram intake-new
knock sensors-new
removed and disconnected oil sensor and replaced with aftermarket sensor
fuel filter-newish
boshe fuel pump-newish
Boshe front and aft O2 sensors-new
IPD turbo back exhaust- new
and of course all new internals
this build is to expensive to let sit any longer. any help or ideas would be much appriciated. thank guys

 

Here is the spark plug order. I read that some manual has it wrong.

 

That is what I was thinking....Spark plug order. Are you SURE you are not 180 out on timing? Starting and idling, but rough/backfire when revved is a classic symptom of that.

 

i lined up the mark on the crank to block and had a screw driver in the cylinder to verify that it was at TDC. If it was 180 out on the crank I believe it wouldnt start at all right? i mean at least itll run on its own for a minute or two. and if i have a cam 180 out it would simply tear up my valves. but i am going to check my spark plug wires today as seeing this is the second forum to tell me they think its those.

 

Yep, ck the spark plug wire order. If cams are timed correctly (did you put in different cams by chance, or have the sprockets off?) and the plug wires are correct, the only other thing (that would cause backfires) might be a rather large air leak; forget the intake manifold gasket by chance?

 

ok so today I double check the ignition system in this order:
-pulled the plugs, turned over the car and watched the sparks go in the exact order they are supposed too.
- put cyl no. 1 at tdc then pulled distributor cap and checked to see if rotor was at no. 1 wire and it was. so that told me my intake cam is lined up correctly regardless of the marks on the cam gear.

I double and triple checked the timing again and the exhaust cam is just the next valley off. so not even one tooth. that wouldnt make it run that bad i would think?

I checked and yes i made sure i had my manifold gasket lol but i did find two bolts on the bottom inside part of the manifold that i forgot to put bolts into. im trying to find bolts to fill those holes.

just throwing some ideas out. maybe MAF? or maybe swapped O2 sensors? possibly fuel injectors maybe getting stuck open since my plugs are kinda wet when i pull them.

Thanks for advice, it has me thinking differently.

 

Ok so I double checked that I had spark and my no. 1 and 2 cyl. Didn't! It was going in and out with spark then I tested the wires to measure ohms and it was fine then I cleaned the points and then they never sparked again. But the other three spark good. Did I take to much material off on the points? Or not enough. It had carbon build up on all points. I don't see how since the ignition system is only 40,000 miles old.

 

Umm, what "points" are you talking about?

 

From what you say the cap rotor and wires are new but it sounds like the cap or wires are defective. It's about the only cause of having one or two plugs loose spark while the others are still working.

Since the standard plugs are copper core that's just about where you'd be replacing the second set of plugs. How many miles do you think a cap and rotor are good for ?? Is the cap and wires set new or is that what has 40K. If it's 40K you need a cap and rotor and retest for spark at the plug on all five.

Wires are a finicky thing. They may test good one way and if you bend them a bit in a different direction you find you have a break in the conductor or in the insulation.

What did you use to scrape the points and are you talking about the contacts inside the cap ?? I've used a screwdriver to scrape off build up or scale off the contacts but if you're doing that then you have worn and needing replacement parts. I always recommend cap and rotor together.

 

Ok so an update. I replaced my cap to see if that would eliminate the no spark problem and it did. So I was happy. Now though, spark all looks good except no. 3 spark plug sparks out of sequence. It seems to spark more frequently then the others. It'll be in sequence for a few seconds then go back out. The only thing I can think of is carbon trails(which I didn't see) or EMF coming from other wires. I tried isolating that wire and it still did it. I'm at a complete loss here.
PS.- "points" to me are the contact points within the distributor cap.

 

I hope someone can jump in and give you a hand as I'd be at a loss to have even a guess about the spark being out of sequence on only one wire, especially with a new cap. Kind of rules out any carbon tracking. If you hadn't said you tried to isolate the wire I'd guess you have a short and the spark from an adjacent wire is jumping.

I'd like to see some video of it

 

another update. something is still funky with the spark. all cylinder head temps are at normal temperature. but still runs rough. compression on all cylinders when cold is at 160psi. keep in mind, I honed cylinders, new rings, and lapped valves. Not exactly sure what good compression for these engines should be.
Also we stopped after we turned it over a couple times and the dipstick and oil cap literally blew in the air. I do know what causes that. lol I prolly got the two hoses backwards on the the flame trap box thats under the intake manifold.

 

Sorry Man, I am not going to be much help; you're talking some kind of different jive that I'm not hip to, Man...

No contact points in the distributor cap; if those "points" are making contact, you got serious problems..

 

Well what is your definition of "points"? like where are they located?

 

It would depend on your age and depth of automotive knowledge. The common understanding of the term "points" with no other context to narrow it down would be the contact points inside the distributor that trigger the secondary circuit to fire. It's pretty universal. The things inside the distributor aren't points in any ones definition that I know of, they are referred to as contacts.

 

New rings would be expected to have plenty of blow-by before they "seat".