Tylerj Posted July 31 Share Posted July 31 Hey guys I’ve been lurking for awhile and doing as much research as I can without asking for a little advice. I have an 05 a1-400 that I just bought and has a slight stumble when you rev it. It clears up at about 1200 rpm and runs fine after that. The truck also only gets about 3.5 mpg. It black smokes a little when you start it and a tiny bit when you rev it but not thick. I’ve read that injectors lose performance around 5000 hours and the truck has about 25000 on it now. Looking back at all the service records it doesn’t appear that the injectors have ever been replaced. Do you guys think it’s worth buying a pop tester and test them or should I just replace them since there’s so many hours on them. Also who do you guys recommend for injectors? Thanks for any info. Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/ Share on other sites More sharing options...
Tylerj Posted July 31 Author Share Posted July 31 Forgot to mention after a long trip it formed a small amount of oil coming from the pencil tube and the fitting going into the head. I don’t know if this matters or not. Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556165 Share on other sites More sharing options...
Joey Mack Posted July 31 Share Posted July 31 Is it oil? Is it only coming from around the threads on the injector line? Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556187 Share on other sites More sharing options...
fjh Posted July 31 Share Posted July 31 12 hours ago, Tylerj said: Forgot to mention after a long trip it formed a small amount of oil coming from the pencil tube and the fitting going into the head. I don’t know if this matters or not. Its not worth buying a pop tester unless you know what your looking for ! it is worth pulling the injectors and either rebuilding them or replace them with exchange! The oil could be evidence that the top oring is failing in the injector ! Just my opinion! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556192 Share on other sites More sharing options...
Tylerj Posted July 31 Author Share Posted July 31 1 hour ago, fjh said: Its not worth buying a pop tester unless you know what your looking for ! it is worth pulling the injectors and either rebuilding them or replace them with exchange! The oil could be evidence that the top oring is failing in the injector ! Just my opinion! Yes it’s oil, it’s a tiny buildup but it’s not coming from the threads it’s coming from in between the pencil tube and the fitting itself. I read the whole thread that Mack technician that you were involved in. I’ve contacted k and s on injectors but have also sourced new Bosch, I’m not sure which is the better route. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556195 Share on other sites More sharing options...
Joey Mack Posted July 31 Share Posted July 31 I would pull the valve cover and see if the injector hold down cap is loose. They torque to 50 lbft Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556197 Share on other sites More sharing options...
Tylerj Posted July 31 Author Share Posted July 31 Thanks will do. Do you recommend new or get these rebuilt? Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556198 Share on other sites More sharing options...
Joey Mack Posted July 31 Share Posted July 31 Hard tellin'. Im not against rebuilding. I guess personal preference and wallet size will decide. Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556201 Share on other sites More sharing options...
The Heinz Posted July 31 Share Posted July 31 1 hour ago, Tylerj said: Thanks will do. Do you recommend new or get these rebuilt? We have seen a couple reman injectors bad out of the box, but it's not a regular occurrence. I'd price it out to see which one comes out cheaper, just make sure you use a reputable rebuild shop. Our local shop was cheap enough that even after our system marked the price up, it was cheaper than the injector itself. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556202 Share on other sites More sharing options...
Tylerj Posted July 31 Author Share Posted July 31 1 hour ago, Joey Mack said: Hard tellin'. Im not against rebuilding. I guess personal preference and wallet size will decide. The price difference isn’t much different getting mine rebuilt from k and s or buying new Bosch units. K and s said I’d get more hp out of them if I sent him mine and had him do them. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556204 Share on other sites More sharing options...
fjh Posted August 1 Share Posted August 1 Search out this post if you’re interested in regaining power and fuel mileage! A little pricey but ……. if you want to spend money on a good fix ! The main issue with the ai engine is you have to keep it wound out to make any decent power it can’t breathe! Mack AI460 AI427 AMI low torque low horsepower poor fuel mileage granite , dead dog , remediation Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556245 Share on other sites More sharing options...
Tylerj Posted August 1 Author Share Posted August 1 12 hours ago, fjh said: Search out this post if you’re interested in regaining power and fuel mileage! A little pricey but ……. if you want to spend money on a good fix ! The main issue with the ai engine is you have to keep it wound out to make any decent power it can’t breathe! Mack AI460 AI427 AMI low torque low horsepower poor fuel mileage granite , dead dog , remediation I actually read that whole thread, I learned a ton! I’m gonna start with injectors and go from there, I would like to do the 5” exhaust to keep egts down but those exhaust pieces are over 500$ now!!! I may end up building one for it though Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556260 Share on other sites More sharing options...
JoeH Posted August 1 Share Posted August 1 I'd pull the EUP's and also their respective can followers. I just had some major work done on my 2003 ai-350 with 28,000 hours. Had stumble/miss/low power. 3 bad EUPs, 2 had broken springs (1 spring was broken in 5 pieces....) truck also had 2 bad EUP Cam Followers and 1 bad injector nozzle. Cam followers, roller axle shifted on one, cocking the roller so it didn't ride smooth on camshaft. Other bad follower had a chip out of the top of the cup from broken EUP spring. I think the Cam Followers from Bosch through Metro Fuel Injection/M&D were around $150 each, and the reman EUP's were in the $500+ range after good cores returned. In hindsight I should have replaced all 6 followers and at least tried to replace the springs on the 3 EUPs I didn't replace, but we were very tight on money. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556262 Share on other sites More sharing options...
Tylerj Posted August 7 Author Share Posted August 7 On 8/1/2024 at 8:55 AM, JoeH said: I'd pull the EUP's and also their respective can followers. I just had some major work done on my 2003 ai-350 with 28,000 hours. Had stumble/miss/low power. 3 bad EUPs, 2 had broken springs (1 spring was broken in 5 pieces....) truck also had 2 bad EUP Cam Followers and 1 bad injector nozzle. Cam followers, roller axle shifted on one, cocking the roller so it didn't ride smooth on camshaft. Other bad follower had a chip out of the top of the cup from broken EUP spring. I think the Cam Followers from Bosch through Metro Fuel Injection/M&D were around $150 each, and the reman EUP's were in the $500+ range after good cores returned. In hindsight I should have replaced all 6 followers and at least tried to replace the springs on the 3 EUPs I didn't replace, but we were very tight on money. Is there a way to test the EUP’s? I have injectors already. The truck doesn’t run bad just not like I think it should, I am going to pull the EUP’s when I do the injectors just to make sure the look good but I’m not sure there’s anyway to manually check them. With new EUP’s I have to program them to the computer correct? Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556591 Share on other sites More sharing options...
Joey Mack Posted August 7 Share Posted August 7 EUP's are resilient... Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556592 Share on other sites More sharing options...
fjh Posted August 7 Share Posted August 7 13 hours ago, Joey Mack said: EUP's are resilient... yup how ever them springs can break as pointed out !worth a look see! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556632 Share on other sites More sharing options...
JoeH Posted August 7 Share Posted August 7 No need to calibrate trim codes. My truck is running just fine without them. You can pull a wire off one EUP at a time while idling and see if the idle changes. Screw can't be removed, just loosen it a bit and the wire can be lifted off. You'll get a spark, no big deal. If one EUP doesn't affect the idle then that one is faulty or the wiring is faulty. But this test won't reveal broken springs. You've got to pull the EUP's and also their followers. Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556635 Share on other sites More sharing options...
Tylerj Posted August 7 Author Share Posted August 7 12 minutes ago, JoeH said: No need to calibrate trim codes. My truck is running just fine without them. You can pull a wire off one EUP at a time while idling and see if the idle changes. Screw can't be removed, just loosen it a bit and the wire can be lifted off. You'll get a spark, no big deal. If one EUP doesn't affect the idle then that one is faulty or the wiring is faulty. But this test won't reveal broken springs. You've got to pull the EUP's and also their followers. Perfect I will try that before I replace the injectors this weekend. I had planned to pull them out and check over them but I wasn’t sure on testing them. Thank you for the info I will let you know what I come up with. Quote Link to comment https://www.bigmacktrucks.com/topic/74401-stumble-on-acceleration/#findComment-556637 Share on other sites More sharing options...
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