Rough Running Sound

[Splashsky]

I have my '91 4R running now, and it idles decently at around 800/900 RPM before dipping down to 400/500.

There's this rough sound coming from the engine while it's running, like it's missing. Part of the sound is from the exhaust not being completely hooked up, but the majority would be from the engine.

Here's a video of it. Does anyone have any ideas? I've double- and triple-checked timing (marks on the crank and cam pulleys), the distributor lines have been checked and lined up with the first cylinder at TDC in the compression stroke, with the MAF and TP the ohms tested good, spark's been verified, as well as fuel delivery.

The one troubling fact is the compression in the No.1 cylinder is 115; I'll update the post with the other five cylinders once I check them. According to TIS, the compression range is 145 to 171, so there's a problem with compression there.

Really need some advice on how to proceed. If anyone would like to call or talk to me, please PM me.

 

[4bt40]

Dang that thing sounds like a cammed V8 lol..
Have you used a timing light on it? It definitely seems like an ignition issue. That terrible shake makes it look like its down a cylinder. You are 100% you have good spark at each plug? I can only imagine that the compression in that one cylinder is exacerbating the issue, if not the entire issue itself. Good luck.

 

[541joseph]

Start it and pull plug wires one by one and replace until you find the one that it doesn't make a difference then trace the wire and you know what one is your issue. Almost sounds like the distributor is a tooth off

 

[Walter Gropius]

My 86 mazda has started to run pretty rough. It acts like its missing. I checked the Coil and it appeared to be bad as he was putting out a orange spark instead of a blue one so I replace it.