I have a 1983 Mercury Capri turbo RS. I have been chasing a surging problem under boost for quite some time. The car has the biggest after-market SVO turbo catalog cam (available circa 1994) along with a ported head and oversized intake and exhaust valves. It has the 83 inline intake which has been port matched but retains the stock throttle body. About 15 years ago it got injectors from an 85.5 SVO and computer and air meter. I have tried multiple computers including an 86 PE SVO computer and the original 83 Capri rs computer. In all cases under boost the car tends to Surge.It then has been more recently updated to have an 88 Thunderbird Turbo Coupe air meter (basically the same as the svo meter but was trying to troubleshoot) and la3 computer. Same results.
I have it limited currently to only 10 psi and have checked my fuel pressure with it being at about 36 PSI at idle and going up to about 45 PSI under boost. I have disconnected the knock sensor and it helped some but in the grand scheme it made little change.
I have pulled codes and only have a code for the knock sensor which is unplugged. I'm turning to The Experts for ideas on what to try next and how to isolate the problem. It feels like either the timing is retarding on about a one and a half second interval or the fuel map is coming up and down on the same cycle. The motor is not missing it just seems too lose and then regained power every second to Second and a half.
Thoughts?
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