90 RRC stumble at 3000 RPM

az_max

1
Apr 22, 2005
7,463
2
Driving uphill I have a stumble around 3000 RPM *. When the trans downshift because of the hills, the tach goes from 2k to 2800 or so, around 3000 the engine stumbles or cuts out briefly. If I back out of the throttle, I can keep it around 2800 or so.
I'm thinking spark. Coil, Cap and wires are new within the year. Dist Amp is old, maybe original. I tried putting a remote amp in last year, but was unsuccessful and had to revert to the original. I'm going to have to do some work to measure fuel pressure, voltage at the coil etc, to solve this.


* (Towing 1000 lbs, 4-5% upgrade going from 3000 to 6000 ft. I got passed by motor homes and schoolbusses)
 

Tugela

Well-known member
May 21, 2007
4,754
562
Seattle
Interesting. I had something similar happen yesterday on my 1993. Cruising on level highway and engine stumbled. It was like a surge or interruption in power. Happened between 60-65mph, maybe 2,500 RPM. It continued for a couple miles until I could exit the highway. Driving home on surface streets the engine ran fine.

I recently bought the truck so I'm still learning its quirks. I have documentation from previous owner of complete engine replacement 5 years ago. Distributor looks new, wires have a couple cracked rubber boots on distributor end.

I was planning to replace the spark plugs and wires and fuel filter this weekend anyway. On that note, will the Kingsbourne wires I bought for my GEMS Disco fit my RRC? The connections should be standard, but the lengths might be different.
 

XCELLER8

Well-known member
Sep 21, 2009
249
12
for both of you guys, I would try a new coil....those are classic coil breakdown symptoms, even if it's a relatively new coil.....I had 2 new Bosch coils fail witin 3 months
 

Tugela

Well-known member
May 21, 2007
4,754
562
Seattle
For those of us who are recent arrivals to the world of 14CUX, could you please elaborate on coils? On my GEMS truck I know coils as the the ignition component that's mounted in a bank behind the upper plenum to which the other ends of the spark plug wires connect. What is it, where is it, and how do I inspect/test it on the RRC?
 

Tugela

Well-known member
May 21, 2007
4,754
562
Seattle
Took a look at the coil today while replacing my spark plugs and wires. It is easily accessed and appears to be a straightforward swap. Before I order a replacement do you have any recommendations on which to buy? The one currently in my truck is a Bosch, you say you've had two of those fail. What has been the most reliable for you? The Lucas coil is considerably cheaper but I'm not sure I need any more Prince of Darkness parts in my electrical system, and I've found a couple different Bosch options. Pointers appreciated before purchase.