# Hunting for Power Loss (maybe) **URL:** \ **Category:** Diagnostics & OBD Codes\ **Tags:** trooper\ **Created:** [July 8, 2026, 11:46pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169 "2026-07-08T23:46:46Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 8, 2026, 11:46pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/1 "2026-07-08T23:46:46Z")
**Before you post, fill this in — it gets you answers faster:** - Year:91 - Model:Trooper - Engine:2.6 - Transmission:5 speed - What changed recently (if anything): nothing - Symptoms / what it’s doing: Seemingly has a lack of power - Codes (if any): no - What you’ve already tried: Check’d Vacuum lines and for brake drag _(Add at least one tag for the system or engine involved.)_ ![image](https://forum.isuzunation.com/uploads/default/original/1X/baac04df7a608d8e1d67e375294828415e05ebe3.jpeg) As I keep slowly fixing / upgrading this 91 I got, I seem to have intermittent power changes. Some mornings it runs great, pulls great all the way through the rev range etc, other mornings / afternoons it really feels like its choked around 3k and falls over. One afternoon running through the hills, I had to bounce between 2nd & 3rd because I didnt have enough oooomph to keep speed in 3rd. As seen in the picture above, it has 31’s on it, jerry cam, and ~250 lbs of tools and camping shit in the back. I am getting ready to build my drawer system so the full camp setup will be ~500 lbs so I need to make sure its running like a top. My todo for fix’n this weekend is as follows: IAC Valve cleaning ? - I assume I can pull and clean (or smack with a hammer) Temp Gauge ? - I read somewhere that these are pretty sensitive to heat on that sensor Vacuum Leak check again - I hear no change when spraying carb cleaner all over the place but will spray another can this weekend to check. Does have a big old exhaust leak at the flex pipe but I had these same issues before and after the grand canyon opened. Maybe valves? I’ve only put 2500 miles on it since I got it from Lorenzo so that is pretty low on my list of causes. Let me know what else I am forgetting to check / remind me I am a bonehead ---
**Author:** ![Cooltrainersamson](https://forum.isuzunation.com/user_avatar/forum.isuzunation.com/cooltrainersamson/32/28_2.png) [@Cooltrainersamson](https://forum.isuzunation.com/u/Cooltrainersamson)\ **Post date:** [July 9, 2026, 12:32am UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/2 "2026-07-09T00:32:24Z")
Welcome to the formum! I’m sure some experts will pipe up soon, but your symptoms had me wondering if it’s a fuel pump that’s going bad? ---
**Author:** ![EdMc34ZuZu](https://forum.isuzunation.com/user_avatar/forum.isuzunation.com/edmc34zuzu/32/32_2.png) [@EdMc34ZuZu](https://forum.isuzunation.com/u/EdMc34ZuZu)\ **Post date:** [July 9, 2026, 12:35am UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/3 "2026-07-09T00:35:57Z")
Or maybe the fuel pressure regulator? Might be time for a fuel pressure test! ![ITEC Fuel Pressure Testing_1](https://forum.isuzunation.com/uploads/default/original/1X/856cac3c54d78dae4a9aa8088bbc180121ad4a4f.jpeg) ![Sean's '88 Trooper_Fuel Pump Jumper Location](https://forum.isuzunation.com/uploads/default/original/1X/6f7d6b551b33bc022759e324f046c128927b873b.jpeg) ![ITEC Fuel System Diagram](https://forum.isuzunation.com/uploads/default/original/1X/5f0f0da5f1681770b157bfd4994e46989d077429.jpeg) ![ITEC Fuel Pressure Testing_2](https://forum.isuzunation.com/uploads/default/original/1X/af9cfa9bc1e20de7889e86c4601e93cf309f6264.jpeg) ---
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 9, 2026, 12:48am UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/4 "2026-07-09T00:48:01Z")
Turner helped me do the fuel pump / clean the tank months ago, Also had the regulator replaced New fuel filter as well. Will still check the regulator as a precaution ---
**Author:** ![EdMc34ZuZu](https://forum.isuzunation.com/user_avatar/forum.isuzunation.com/edmc34zuzu/32/32_2.png) [@EdMc34ZuZu](https://forum.isuzunation.com/u/EdMc34ZuZu)\ **Post date:** [July 9, 2026, 12:53am UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/5 "2026-07-09T00:53:27Z")
Take 'er out and when she starts acting up, find a place to pull over quick and pull the spark plugs. You can tell a lot by their coloration. You might have one that’s white (running lean), or sooty (rich). Ideally you’ll get a light tan or similar. Check spark quality, when cold and then when it’s acting up. You should have a hot, purplish spark coming out of the ign coil. It the spark is red or yellow, that’s weak. Also check the distributor cap and rotor. A failing rotor can arc to ground and cause all sorts of strange behavior. ---
**Author:** ![itsmehb](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/i/8491ac/32.png) [@itsmehb](https://forum.isuzunation.com/u/itsmehb)\ **Post date:** [July 9, 2026, 10:13am UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/6 "2026-07-09T10:13:30Z")
There is one thing that’s easy to check. Assuming we are talking 2.6 engine, the intake pipe where it runs over the valve cover will sometimes rub against the valve cover and over time will wear a hole in the pipe. Ask me how I know? This lets intake air in after the sensor (map) that measures and sends that info to the engine computer. That causes the wrong signal to the injectors that pulse fuel and will cause symptom’s like your having. Worth a look. ---
**Author:** ![2zuzus](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/2/58f4c7/32.png) [@2zuzus](https://forum.isuzunation.com/u/2zuzus)\ **Post date:** [July 9, 2026, 9:44pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/7 "2026-07-09T21:44:07Z")
If your machine was running as nice as it looks, you would be flying up hills. With the talent here, you’ll be flying soon. Welcome to a great site! ---
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 9, 2026, 10:06pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/8 "2026-07-09T22:06:21Z")
Went out after work and fiddled, looks like the line coming from the bottom of the IAC to the bottom of the intake had partially collapsed. The IAC was relocated to the side of the intake where that bottom bolt is. This forces you to use a longer line which, over time, seems to have weaked and “Creased” preventing full flow. Looks like a 12.7mm hose and all I had at the house was 11.X, I will run by the parts house tomorrow and grab the correct diameter hose and replace. Hopefully this is the issue. No wearing on the intake tube anywhere from MAF back to intake. ---
**Author:** ![Cooltrainersamson](https://forum.isuzunation.com/user_avatar/forum.isuzunation.com/cooltrainersamson/32/28_2.png) [@Cooltrainersamson](https://forum.isuzunation.com/u/Cooltrainersamson)\ **Post date:** [July 9, 2026, 10:37pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/9 "2026-07-09T22:37:54Z")
Very awesome! Hopeful that that solves the issue 😃 ---
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 10, 2026, 8:49pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/10 "2026-07-10T20:49:51Z")
So it does appear that the IAC is pulling enough vacuum to collapse the hoses I am trying to use. Can’t tell if the hose is making it he sucking noise or the actual valve unit? Not sure where else to mount it? Maybe closer to the top ? Best I can see is there will be a hard turn no matter where it’s at? Some days I love old vehicles and other days I struggle not to go into crippling debt to buy a newer truck, today is the latter ---
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 11, 2026, 4:52pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/11 "2026-07-11T16:52:31Z")
![1408](https://forum.isuzunation.com/uploads/default/original/1X/95104ddf8f96ec85a06965b6842b41cc2413e927.jpeg) ![1412](https://forum.isuzunation.com/uploads/default/original/1X/bf281f67e699ca4d6209fb5b1220da4002fdfa4b.jpeg) ![1411](https://forum.isuzunation.com/uploads/default/original/1X/74fcbee93a3ca1c2fc34b336507cba456d76321f.jpeg) ![1410](https://forum.isuzunation.com/uploads/default/original/1X/ba4a5807c9ea1b928ee936d33d0933796c0d803a.jpeg) ![1409](https://forum.isuzunation.com/uploads/default/original/1X/10539dcbad9e4c398b466e73f5e472dce04fefbb.jpeg) Plugs look fine to me? ---
**Author:** ![AuDmax](https://forum.isuzunation.com/user_avatar/forum.isuzunation.com/audmax/32/33_2.png) [@AuDmax](https://forum.isuzunation.com/u/AuDmax)\ **Post date:** [July 11, 2026, 5:13pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/12 "2026-07-11T17:13:06Z")
Agreed… ---
**Author:** ![2zuzus](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/2/58f4c7/32.png) [@2zuzus](https://forum.isuzunation.com/u/2zuzus)\ **Post date:** [July 12, 2026, 3:11pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/13 "2026-07-12T15:11:26Z")
Since there is vacuum, is that a reinforced hose to start with? If not, something like heater hose or fuel line may help. Where there is a hard turn, can you cut the line and use rigid material (plastic or metal piping) to make the bend? Also, if there is room, doing a partial full circle (that prevents a pinch) with hose can get the job done. Anything to prevent getting a new chocked-with-electronics vehicle, LOL. ---
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 12, 2026, 3:27pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/14 "2026-07-12T15:27:48Z")
The hose I have is a heater hose, but it still collapses about 90%. I have a rigid vacuum rated hose coming in from chinazon today. Ill probably also order 2 90’s and do that at the bottom incase that doesnt work. Spent the morning doing the oil, trans, and tcase flush. Looks like the fill plug for the trans is stripped so I need to grab a washer and teflon tape to fix that small leak. ---
**Author:** ![Cooltrainersamson](https://forum.isuzunation.com/user_avatar/forum.isuzunation.com/cooltrainersamson/32/28_2.png) [@Cooltrainersamson](https://forum.isuzunation.com/u/Cooltrainersamson)\ **Post date:** [July 12, 2026, 3:31pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/15 "2026-07-12T15:31:16Z")
Heck yeah! Let us know if you end up fixing it 😌 ---
**Author:** ![2zuzus](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/2/58f4c7/32.png) [@2zuzus](https://forum.isuzunation.com/u/2zuzus)\ **Post date:** [July 12, 2026, 4:09pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/16 "2026-07-12T16:09:41Z")
Wow! That is some vacuum to collapse a heater hose that far. Is there an obstruction on the other end that is not letting sufficient air move through the hose? Good that you have the chinesium hose on order. Too bad about the stripped plug. Usually it’s the softer aluminum though, so you dodged that bullet. I tend to coat my steel fasteners going into aluminum with never-seize because of that galvanizing factor between dissimilar metals. Good you have a repair to seal it. Keep us posted. ---
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 12, 2026, 4:56pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/17 "2026-07-12T16:56:31Z")
Not that I can tell, comes straight up and over → IAC → down and back up to the intake. Will update once the new hose is on / If it fixes the lack of power issue. Gonna get a new one on order already so I guess I’ll throw that at it once it comes in. From what I can tell, there are no vacuum issues on the top side. Sprayed the shit out of it with carb cleaner and never had a rev change. ![1414](https://forum.isuzunation.com/uploads/default/original/1X/1324b6c323327248caf6d10eca367b6f09085283.jpeg) ![1416](https://forum.isuzunation.com/uploads/default/original/1X/76176c3d2d69e90d156fbaf008a765a34dd9a6eb.jpeg) ![1415](https://forum.isuzunation.com/uploads/default/original/1X/8d1f6f5327163b182fbe79672f01a5bfc82d3775.jpeg) ---
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 13, 2026, 11:08pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/18 "2026-07-13T23:08:54Z")
IAC → short piece → 90 → short piece → 90 -\>short piece -\>intake That worked, idles gooder now. Still feels down on power, theres a 73 & 2/9th chance I am imagining things. Every day I spend out on this thing after work makes me think I have completely lost it. Whats next? Fuel system (pump, filter, injectors, regulator) have all been fixed so its getting gas Spark is good Still need to take it to get the exhaust done on it, but I dont expect that to matter. Maybe have to hunt again for someone local that wants to fiddle with it / help me / call me stupid (while I pay them) ---
**Author:** ![itsmehb](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/i/8491ac/32.png) [@itsmehb](https://forum.isuzunation.com/u/itsmehb)\ **Post date:** [July 13, 2026, 11:28pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/19 "2026-07-13T23:28:44Z")
> [@RealJon](#): > > Still need to take it to get the exhaust done on it, but I don’t expect that to matter. You may be surprised. On my 89 Trooper, I took the members experience and had a 2.25 in. pipe along with a gutted cat and a turbo muffler installed. Was a little high (300) but worth it. I noticed an improvement first time I drove it. ---
**Author:** ![RealJon](https://forum.isuzunation.com/letter_avatar_proxy/v4/letter/r/8e7dd6/32.png) [@RealJon](https://forum.isuzunation.com/u/RealJon)\ **Post date:** [July 13, 2026, 11:36pm UTC](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169/20 "2026-07-13T23:36:03Z")
Ill call around and see if I can get a shop to do it tomorrow. [Next page](https://forum.isuzunation.com/t/hunting-for-power-loss-maybe/169.md?page=2)