98 S70 T5 Misfire under high acceleration or high speeds.

volvo_bruh · Post by **volvo_bruh** » 21 Nov 2015, 13:46

I've been having a misfire issue on my car for about a month now. I replaced my rear cam seals and during the process, I broke my distributor cap but I was doing the job out of town in a friend's garage so I had to replace it with a cheap Auto Zone cap. I assumed the misfire was from this cheap Auto Zone cap so I replaced it with the original Bosch cap. Misfire seemed to be gone but it came back last night. At heavy acceleration it pulls strong like it usually does but once it gets up to a certain speed like past 90 mph it stutters. I did one more pull and brought it up to 120 mph and it stuttered quite a bit with the CE light flashing so I've been driving easy on it since. It only misfires in these situations, otherwise it runs perfectly fine. Rotor seems to be fine, cap is new, and I'm running IPD spark plug wires. I don't wanna start throwing parts at it because I think if it was a bad component, it would run like garbage all the time and that isn't the case. My other concern is that I did a manual swap on it over the summer and I've been running the original ECU which I heard isn't the best for the car. The only modifications I've done as far as the engine is I switched from the stock injectors to the blue ones and I turned the boost up manually to around 12-14 pounds. Is it time for a tune or is it because I'm still running this auto ECU? Or both? It ran fine and pulled fine at high speeds before I did the cam seals and origianlly broke the distributor cap. Am I missing something?

Post by **rspi** » 21 Nov 2015, 17:31

Have you checked timing and spark plug gap?

volvo_bruh · Post by **volvo_bruh** » 21 Nov 2015, 18:29

I haven't touched the timing or messed with the spark plug gap. I was thinking about putting 5 fresh OEM plugs in. I did my timing this past February, replaced it with a Gates racing belt and a new ttensioner. How do I check the gap?

Post by **Matty Moo** » 21 Nov 2015, 18:51

How old are the plugs in there? What kind?

Post by **rspi** » 21 Nov 2015, 20:20

Spark plug gap tool, at 5:40. Also, it is possible to jump time while screwing with the cam seals.

volvo_bruh · Post by **volvo_bruh** » 21 Nov 2015, 23:25

How do I know if I jumped time? I had the reluctor wheel in wrong when I put it back after doing the exhaust cam seal. It took 3-4 tries of tearing it apart and putting it back in another way. After putting it in the last time, it fired right up like it always does.

Post by **erikv11** » 22 Nov 2015, 07:12

Negative, there is no way to mess up the timing from monkeying with rear cam seals, cross that one off the worry list.

Post by **rspi** » 23 Nov 2015, 13:25

volvo_bruh wrote:How do I know if I jumped time? I had the reluctor wheel in wrong when I put it back after doing the exhaust cam seal. It took 3-4 tries of tearing it apart and putting it back in another way. After putting it in the last time, it fired right up like it always does.

You pull the timing belt cover and make sure all 3 marks are aligned.

Post by **rguzz** » 23 Nov 2015, 14:54

You should at least consider over boost as a cause of "misfire" under open throttle. I experienced stuttering under load did basic tuning then was left with cutoff under wot. So I will be exploring the usual overboost suspects. My stock boost gauge was all the way pegged when malfunction occurred, another clue for me.